Abstract
Introduction
High-quality epidemiologic research is essential in reducing chronic diseases. We analyzed the quality of systematic reviews of observational nontherapeutic studies.
Methods
We searched several databases for systematic reviews of observational nontherapeutic studies that examined the prevalence of or risk factors for chronic diseases and were published in core clinical journals from 1966 through June 2008. We analyzed the quality of such reviews by using prespecified criteria and internal quality evaluation of the included studies.
Results
Of the 145 systematic reviews we found, fewer than half met each quality criterion; 49% reported study flow, 27% assessed gray literature, 2% abstracted sponsorship of individual studies, and none abstracted the disclosure of conflict of interest by the authors of individual studies. Planned, formal internal quality evaluation of included studies was reported in 37% of systematic reviews. The journal of publication, topic of review, sponsorship, and conflict of interest were not associated with better quality. Odds of formal internal quality evaluation (odds ratio [OR], 1.10 per year; 95% confidence interval [CI], 1.02-1.19) and either planned, formal internal quality evaluation or abstraction of quality criteria of included studies (OR, 1.17 per year; 95% CI, 1.08-1.26) increased over time, without positive trends in other quality criteria from 1990 through June 2008. Systematic reviews with internal quality evaluation did not meet other quality criteria more often than those that ignored the quality of included studies.
Conclusion
Collaborative efforts from investigators and journal editors are needed to improve the quality of systematic reviews.
Introduction
Valid epidemiologic research is essential in preventing chronic diseases (1-3). Assessing the quality of observational studies is an important part of evidence synthesis (4). Systematic reviews have become key tools in evidence synthesis from a growing number of epidemiologic studies (5). Producing high-quality systematic reviews is essential to developing generalizable and actionable conclusions (6,7). Quality criteria for systematic reviews have been proposed by working groups that developed the Meta-analysis of Observational Studies in Epidemiology (MOOSE), Strengthening the Reporting of Observational Studies in Epidemiology (STROBE), and a measurement tool for assessment of multiple systematic reviews (AMSTAR) (8-12). The working groups and the Cochrane handbook (13) addressed those criteria for systematic reviews that more likely result in biased results, including bias in selection of the studies or the information within studies by the reviewers (14-18) or bias in the publication of positive significant results (6,15,19,20).
Previous research and guidelines (13,21-23) focus on systematic reviews of interventional therapeutic studies. Validity of observational nontherapeutic studies of prevalence of chronic diseases or risk factors for diseases is essential for effective preventive public health actions (24,25). Our aim was to evaluate the quality of systematic reviews of observational nontherapeutic studies that examined the incidence and prevalence of chronic conditions and risk factors for diseases. The criteria we used to determine the reporting and methodologic quality in systematic reviews were from published standards (8-12). We hypothesized that the quality of systematic reviews differs by the time when the study was published, the country in which the study was conducted, the journal of publication, the sponsorship of the study, and whether a conflict of interest was disclosed. We hypothesized also that systematic reviews with internal quality evaluation of the included studies would have better quality, demonstrating commitment to quality of evidence.
Methods
Data sources
We searched MEDLINE via PubMed and via Ovid MEDLINE, the Cochrane Library (26) and working groups, WorldCat (27), and Scirus (28) to find systematic reviews of observational nontherapeutic studies published in English from 1966 through June 2008 in core clinical journals (exact search string is listed in Appendix Table 1). We used the definitions of core clinical journals from the Abridged Index Medicus (119 indexed titles). We defined observational nontherapeutic studies as observations of patient outcomes that did not examine procedures concerned with the remedial treatment or prevention of diseases (29).
Study selection
Three investigators independently decided on the eligibility of the studies according to recommendations from the Cochrane Handbook for Systematic Reviews of Interventions (13). We reviewed abstracts to exclude comments, expert opinions, letters, case reports, systematic reviews of interventional studies, and systematic reviews of studies of diagnostic accuracy of tests.
Data extraction
Evaluations of the studies and data extraction were performed independently by 2 researchers. Predefined categorical responses to the checklist items were abstracted into our spreadsheet. Errors in data extraction were assessed by a comparison of the data charts with the original articles (13,30). Any discrepancies were discussed and resolved. The quality criteria that we abstracted were based on guidelines for determining the reporting and methodologic quality of systematic reviews (8-12).
To evaluate selection bias, we abstracted whether the authors of systematic reviews described the search strategy (yes, no, or partially); yes indicated that the authors reported time periods of searches, searched databases, and exact search string. We abstracted whether the authors of systematic reviews described study flow (yes, no, or partially); yes indicated that the authors reported the list of retrieved citations, the list of excluded studies, and justification for exclusion.
We abstracted as dichotomous variables whether the authors of systematic reviews did any of the following:
Stated the aim of the review and the primary and secondary hypotheses of the review.
Included or justified exclusion of articles published in languages other than English.
Searched for gray literature, including abstracts and unpublished studies, to evaluate publication bias (21).
Described any contact with authors of the included studies.
Analyzed sponsorship of and conflict of interest in the included studies.
We abstracted how the authors of systematic reviews described obtained statistical methods with justification and models for pooling with fixed or random effects models in sufficient detail to be replicated (no pooling, random, or fixed). We abstracted whether the authors of pooling analyses reported statistical tests for heterogeneity and whether heterogeneity was statistically significant (not reported, not significant, or significant).
We used 3 categories to classify whether the authors of systematic reviews had evaluated the quality of included studies by using developed or previously published checklists or scales (31): 1) the authors stated planned, formal internal quality evaluations; 2) the authors abstracted selected criteria of external or internal validity without using a planned, formal, and comprehensive internal quality evaluation; and 3) the authors did not conduct internal quality evaluations. We further categorized the studies that evaluated quality criteria to compare studies with no mention of internal quality evaluation of the included studies. We also compared studies with and without planned formal internal quality evaluation. We abstracted with dichotomous responses blinding and reliability testing (reported or not reported) of internal quality evaluations.
We abstracted several explanatory variables that could be related to the quality of systematic reviews:
The year of publication, defined as a continuous variable. We created categories of 4- or 5-year periods: 1990 to 1994, 1995 to 1999, 2000 to 2004, and 2005 through June 2008.
The journals of publication.
The country where the systematic reviews were performed.
The sponsorship of the reviews. Those that had either governmental or foundational support or were fellowships were defined as having nonprofit support.
The disclosure of conflict of interest by authors of reviews (either not disclosed, disclosed as no conflict of interest, or disclosed conflict of interest).
The number of disclosed relationships with industry, defined as a continuous variable.
The sponsor's participation in data collection, analysis, and interpretation of the results of the review.
The review outcomes as risk factors for prevalence or incidence of chronic conditions or diseases.
Data synthesis
We summarized the results in evidence tables. We used prespecified categories of dependent and independent variables and did not force the data into binary categories for definitive tests of significance. We used univariate logistic regression to examine the association between internal quality evaluation and the year of the publication by using the Wald test. Odds ratios (ORs) were calculated with binary logit models and Fisher's scoring method technique. We computed the fractions of systematic reviews meeting various quality criteria in each of the 4 time periods considered. The proportions of systematic reviews that met different levels of each quality criterion were evaluated by using χ2 tests and Fisher's exact tests in cases of small numbers. All calculations were performed at 95% confidence intervals (CIs) by using 2-sided P values with SAS version 9.1.3 (SAS Institute Inc, Cary, North Carolina).
Results
We found 145 eligible systematic reviews of observational nontherapeutic studies (study flow in the Appendix Figure) (32-176). The number of published systematic reviews increased from 17 during 1990-1994 to 56 during 2005-2008. Most of the studies were conducted in the United States (55 publications) or in the United Kingdom (28 publications) (Appendix Table 2). Half of the systematic reviews (73 publications) were funded by nonprofit organizations; 56 (39%) reviews did not publish their funding sources, 4 reviews received industry support, and 10 were sponsored jointly by industry and nonprofit organizations. Almost three-fourths (106) of the authors of systematic reviews did not disclose conflict of interest; 35 publications stated that the authors do not have any conflict of interest; and 4 studies were conducted by authors who reported conflict of interest. The studies were published in 49 journals. Most systematic reviews (122 studies) assessed risk factors for chronic diseases, 19 summarized estimates of prevalence or incidence, 2 studies reported prevalence and associations with risk factors, and 2 studies examined levels of risk factors. Most studies reported incidence and risk factors for cardiovascular diseases (46 studies) or cancer (26 studies).
Quality of systematic reviews
Less than half of the studies reported study flow (49%), assessed gray literature (27%), or addressed language bias (29%) (Table 1). Only 2% of reviews abstracted sponsorship of individual studies and none abstracted the disclosure of conflict of interest by the authors of individual studies that were eligible for the reviews. Pooling was performed in 137 studies; of these, 62% used a random effects model; 57% reported detecting significant heterogeneity across the studies; and 19% did not provide any information about statistical heterogeneity in pooled estimates. The proportion of systematic reviews that met quality criteria including study flow, assessment of gray literature, or the abstraction of funding sources of included studies did not show significant trends from 1990 through 2008. The proportion of systematic reviews that assessed language bias increased from 8% during 1995-1999 to 41% during 2005-2008. In later years, more studies reported using random effects models (79% during 2005-2008 vs 39% during 1995-1999) and tests for statistical heterogeneity (89% during 2005-2008 vs 65% during 1995-1999).
Table 1.
Evaluated Criteria | 1990-1994, n (N = 17) | 1995-1999, n (N = 26) | 2000-2004, n (N = 46) | 2005-2008, n (N = 56) | Total, n (N = 145) | P Valuea |
---|---|---|---|---|---|---|
Literature search | ||||||
No information | 0 | 0 | 1 | 0 | 1 | .7 |
Documented partially | 1 | 1 | 3 | 1 | 6 | |
Complete documenting of databases used, exact search strings used, and time periods of searches | 16 | 25 | 42 | 55 | 138 | |
Contact with authors of the included studies | ||||||
No information | 13 | 17 | 31 | 31 | 92 | .4 |
The authors of the review attempted to contact the authors of included studies | 4 | 9 | 15 | 25 | 53 | |
Study flow | ||||||
Study flow not reported | 10 | 15 | 29 | 18 | 72 | .04 |
Study flow partially reported | 0 | 0 | 0 | 2 | 2 | |
Study flow reported with the list of retrieved citations, the list of excluded studies, and justification for exclusion for each study | 7 | 11 | 17 | 36 | 71 | |
Articles published in languages other than English | ||||||
Language bias was not addressed | 15 | 24 | 31 | 33 | 103 | .01 |
Language bias was addressed: the authors included or justified exclusion of the non-English publications | 2 | 2 | 15 | 23 | 42 | |
Gray literature | ||||||
Gray literature was not assessed | 15 | 17 | 36 | 38 | 106 | .25 |
Reporting of the method of handling abstracts and unpublished studies | 2 | 9 | 10 | 18 | 39 | |
Conflict of interest from included studies | ||||||
Conflict of interest in included studies was not abstracted | 17 | 26 | 46 | 56 | 145 | NA |
Sponsorship of the included studies | ||||||
Sponsorship of included studies was not analyzed | 16 | 25 | 46 | 55 | 142 | .45 |
Sponsorship of included studies was analyzed | 1 | 1 | 0 | 1 | 3 | |
Pooled model obtained in the review | ||||||
Pooling was not obtained | 2 | 0 | 4 | 2 | 8 | <.001 |
Fixed effects model was obtained for meta-analyses | 10 | 16 | 11 | 10 | 47 | |
Random effects model was obtained for meta-analyses | 5 | 10 | 31 | 44 | 90 | |
Heterogeneity across included studies | ||||||
Heterogeneity across studies was not reported | 6 | 9 | 7 | 6 | 28 | .04 |
Heterogeneity across studies was not significant | 5 | 6 | 13 | 11 | 35 | |
Heterogeneity across studies was significant | 6 | 11 | 26 | 39 | 82 | |
Formal internal quality evaluation of included studies | ||||||
Planned, formal internal quality evaluation with developed or previously published checklists or scales | 3 | 6 | 20 | 25 | 54 | <.001 |
Some selected criteria of external or internal quality of included studies were abstracted without planned, formal internal quality evaluation | 2 | 3 | 1 | 20 | 26 | |
No internal quality evaluation | 12 | 17 | 25 | 11 | 65 | |
Reliability of internal quality evaluation reported | 2 | 4 | 8 | 18 | 32 | .99 |
Internal quality evaluation was masked | 1 | 1 | 0 | 1 | 3 | .11 |
Abbreviation: NA, not applicable.
P values for overall χ2 test.
Internal quality evaluation
Planned and detailed quality assessment of included studies was reported in 37% of systematic reviews, and 18% abstracted more than 1 criterion of external or internal quality; significant positive trends were reported during the evaluated time (Table 1). Quality assessment was masked in 3 studies. Development of the appraisals, including references to previously published tools, was reported in 32 studies, but only 6 tested interobserver agreement for quality assessment.
Quality of systematic review by explanatory factors
The quality of systematic reviews did not differ much by study location or by the journal of publication. Systematic reviews of prevalence or incidence or risk factors of the diseases did not differ in their quality measures. Sponsorship was not associated with quality of the reviews. The role of conflict of interest was impossible to establish because the authors of 56 reviews did not disclose funding and authors of 106 reviews did not disclose conflict of interest.
Explanatory factors of internal quality evaluation of included studies
The journal of publication, topic of the review, and continent where the review was conducted were not associated with the likelihood of internal quality evaluation. Systematic reviews of risk factors tended to conduct internal quality evaluation of the included studies more often than reviews of incidence or prevalence or of levels of risk factors. Systematic reviews sponsored by nonprofit organizations conducted internal quality evaluations of individual studies more often than reviews that received corporate funding. Systematic reviews that disclosed conflict of interest conducted internal quality evaluation of individual studies less frequently (10 of 39 studies; 26%) than reviews with no disclosure (44 of 106 studies; 42%). Odds of formal internal quality evaluation (OR, 1.10 per year; 95% CI, 1.02-1.19) and either planned, formal internal quality evaluation or abstraction of quality criteria (OR, 1.17 per year; 95% CI, 1.08-1.26) increased over time. Disclosure of conflict of interest by the authors of systematic reviews was not associated with greater odds of internal quality evaluation.
Quality of systematic reviews by internal quality evaluation
Complete documentation of the literature search including time period, databases searched, and exact literature search strings was less common among reviews with planned, formal internal quality evaluation (48 studies, 35%) than among reviews without it (90 studies, 65%) (Table 2). However, reviews that either abstracted selected quality criteria or planned, formal internal quality evaluation reported partial (6 studies) or complete (74 studies) information about the literature search more often than studies that did not evaluate quality of included studies (64 studies). Reviews that did not justify exclusion of non-English studies ignored quality of individual studies more often (72 studies) than reviews with planned, formal internal quality evaluation (31 studies). The same pattern was present for publication bias: the reviews that did not mention gray literature also ignored the quality of individual studies. The reviews reporting attempts to contact the authors of included studies either performed planned, formal internal quality evaluation or abstracted selected quality criteria more often than reviews without such attempts (OR, 2.3; 95% CI, 1.1-4.7). Reviews with complete reporting of study flow performed planned, formal internal quality evaluation or abstracted quality criteria more often (51 studies) than reviews without study flows (20 studies). More than half of systematic reviews without planned, formal internal quality evaluation (44 studies) also did not report study flow.
Table 2.
Quality Criterion | Definition of Formal Internal Quality Evaluation | |||
---|---|---|---|---|
Planned, Formal Internal Quality Evaluation or Abstraction of Some Quality Criteria, n | Neither Planned, Formal Internal Quality Evaluation nor Abstraction of Some Quality Criteria, n | Planned, Formal Internal Quality Evaluation, n | No Planned, Formal Internal Quality Evaluation, n | |
Literature search | P = .04a | P = .004b | ||
No information | 0 | 1 | 0 | 1 |
Documented partially | 6 | 0 | 6 | 0 |
Complete documenting of databases used, exact search strings used, and time periods of searches | 74 | 64 | 48 | 90 |
Contact with authors of the included studies | P = .02a | P = .25b | ||
No information | 44 | 48 | 31 | 61 |
The authors of the review attempted to contact the authors of included studies | 36 | 17 | 23 | 30 |
Study flow | P < .001a | P = .003b | ||
Study flow not reported | 28 | 44 | 17 | 55 |
Study flow partially reported | 1 | 1 | 1 | 1 |
Study flow reported with the list of retrieved citations, the list of excluded studies, and justification for exclusion for each study | 51 | 20 | 36 | 35 |
Articles published in languages other than English | P = .001a | P = .01b | ||
No information | 48 | 55 | 31 | 72 |
Inclusion of non-English studies or justification for exclusion | 32 | 10 | 23 | 19 |
Gray literature | P = .09a | P = .04b | ||
No information | 54 | 52 | 34 | 72 |
Reporting of the method of handling abstracts and unpublished studies | 26 | 13 | 20 | 19 |
Conflict of interest from included studies | ||||
No information | 80 | 65 | 54 | 91 |
Sponsorship of the included studies | P = .44a | P = .18b | ||
No information | 79 | 63 | 54 | 88 |
Sponsorship of included studies was abstracted | 1 | 2 | 0 | 3 |
Pooled model obtained in the review | P < .001a | P = .06b | ||
Not applicable (no pooling) | 6 | 2 | 5 | 3 |
Fixed effects model | 15 | 32 | 12 | 35 |
Random effects model | 59 | 31 | 37 | 53 |
Heterogeneity across included studies | P = .27a | P = .67b | ||
Not reported | 13 | 15 | 9 | 19 |
Heterogeneity was not significant | 17 | 18 | 15 | 20 |
Heterogeneity was significant at least for one association | 50 | 32 | 30 | 52 |
P value for overall χ2 test between planned, formal internal quality evaluation or abstraction of some quality criteria versus neither planned, formal internal quality evaluation nor abstraction of some quality criteria.
P value for overall χ2 test between planned, formal internal quality evaluation versus no planned, formal internal quality evaluation.
The association between quality of systematic reviews and sponsor participation in the data collection, analyses, and interpretation was difficult to analyze because this information was either omitted or reported in various ways. Less than 10% of systematic reviews contained a clear statement that the sponsors did not play any role in gathering the studies or analyzing or interpreting the results and did not influence the content of the manuscript. Other reviews omitted mention of the role of the sponsor in approval of the manuscript or provided a general statement that sponsors did not influence the conclusions or the content of the paper. Two reviews included statements of unconditional or unrestricted sponsorship of the meta-analyses.
Discussion
Our analyses showed that less than half of the systematic reviews of nontherapeutic observational studies that were published in core clinical journals met each quality criterion. Quality of systematic reviews did not improve over time. Planned, formal internal quality evaluations of the included studies was reported in less than half of systematic reviews, but the prevalence of internal quality evaluations has increased during the last decade. Our findings are in concordance with previously published methodologic analyses of systematic reviews that also found inconsistent quality and incomplete internal quality evaluation of individual studies (6). Methodologic analyses of systematic reviews that focused on particular diseases or conditions demonstrated that half of the publications had major flaws in design and reporting. For instance, systematic reviews of therapies for renal diseases failed to assess the methodologic quality of included studies (177). Methodologic analyses of systematic reviews of interventions showed that 69% of those randomly selected in MEDLINE meta-analyses did not analyze quality of trials (22). Most (68%) systematic reviews of diagnostic tests for cancer did not provide formal assessments of study quality (178). We also found that the quality of reviews did not differ among types of studies (incidence or risk factors for diseases), types of diseases, or journal of publication.
Journal commitment to high-quality research, however, was associated with improved reporting quality of the publications. For example, adoption by journals of the Consolidated Standards of Reporting Trials (CONSORT) improved the quality of the publications of interventional studies (179,180). An endorsement of the developed standards for observational studies including MOOSE and STROBE checklists may also improve quality of the publications. We did not analyze how many core clinical journals adopted these standards and how quality of the publications changed depending on this adaptation. Peer review of submitted manuscripts should include quality assessment using validated tools (12).
We could not identify the factors that can explain differences in quality of systematic reviews. The role of sponsorship and conflict of interest could not be estimated because of poor reporting of this information. The quality and reliability of quality evaluation of the included studies is unclear because development of the appraisals was described in a small proportion of systematic reviews (32 of 80 studies), and only 6 of 80 studies tested interobserver agreement for quality assessment. We did not evaluate all reviews of observational studies that were published in epidemiologic journals. However, it is unlikely that the quality of reviews published in other journals would be better than those in core clinical journals. Future research should investigate the factors that can explain differences in the quality of systematic reviews.
Peer reviewed publications of high-quality systematic reviews can provide the best available research evidence for evidence-based public health (24). Evidence-based decisions can improve public health practice in preventing incidence and progression of chronic diseases (25). In our analysis, less than half of the systematic reviews of observational nontherapeutic studies met quality criteria established in the MOOSE, STROBE, and AMSTAR statements. Internal quality evaluation of included studies should be an essential part of evidence synthesis, but only half of the reviews reported such evaluation. Collaborative efforts from investigators and journal editors are needed to improve quality of systematic reviews.
Acknowledgments
This article is based on research conducted by the Minnesota Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, Maryland (contract no. 290-02-0009).
We thank our reviewers David Atkins, MD, John Hoey, MD, and Christine Laine, MD, for reviewing and commenting on the draft; our collaborating experts, Mohammed Ansari, MBBS, Ethan Balk, MD, Nancy Berkman, PhD, Chantelle Garritty, Mark Grant, MD, Gail Janes, PhD, Margaret Maglione, MPP, David Moher, PhD, Mona Nasser, DDS, Gowri Raman, MD, Karen Robinson, MD, Jodi Segal, MD, and Thomas Trikalinos, PhD, for their scientific input throughout this project; and Carmen Kelly, PharmD, our task order officer, and Stephanie Chang, MD, medical officer, at AHRQ for their guidance throughout the project. We also thank librarian Judith Stanke for her contributions to the literature search; research assistants Emily Zabor, candidate for the master of science degree (MS) in biostatistics, and Akweley Ablorh, candidate for MS in biostatistics, for the data abstraction, quality control, and synthesis of evidence; Zhihua Bian, candidate for MS in biostatistics, for her statistical help; Zhiyuan Xu, candidate for MS in applied economics, for his work creating the ACCESS database; Dean McWilliams for his assistance in database development; Qi Wang, research fellow, for her statistical expertise in reliability testing; Susan Duval, PhD, for her help estimating sample size; Marilyn Eells for editing and formatting the report; and Nancy Russell, MLS, and Rebecca Schultz for their assistance gathering data from the experts and formatting the tables, and Christa Prodzinski for quality control of the data.
Appendix
Table 1.
Search Method | No. of Articles Identified |
---|---|
Search strategy for Ovid MEDLINE | |
1. exp Research Design/st [Standards] | 4,303 |
2. exp Chronic Disease/ep [Epidemiology] | 1,619 |
3. exp Urinary Incontinence/ep [Epidemiology] | 1,155 |
4. exp Fecal Incontinence/ep [Epidemiology] | 328 |
5. exp "Sleep Initiation and Maintenance Disorders"/ep [Epidemiology] | 565 |
6. exp Depression/ep [Epidemiology] | 4,700 |
7. exp Depressive Disorder/ep [Epidemiology] | 6,816 |
8. exp Myocardial Infarction/ | 43,531 |
9. 6 or 7 | 11,214 |
10. 8 and 9 | 105 |
11. 2 or 3 or 4 or 5 or 10 | 3,636 |
12. 1 and 11 | 9 |
13. exp Data Collection/mt, st [Methods, Standards] | 36,173 |
14. exp "Bias (Epidemiology)"/ | 25,369 |
15. exp Questionnaires/st [Standards] | 3,879 |
16. exp Evidence-Based Medicine/ | 27,487 |
17. 13 or 14 or 15 or 16 | 86,857 |
18. 11 and 17 | 127 |
19. 12 or 18 | 133 |
20. limit 19 to english language | 124 |
21. exp "Predictive Value of Tests"/ | 62,290 |
22. exp "Reproducibility of Results"/ | 126,475 |
23. 21 or 22 | 182,941 |
24. 11 and 23 | 126 |
25. limit 24 to english language | 121 |
26. 20 or 25 | 224 |
27. exp randomized controlled trial/ | 151,027 |
28. 11 and 27 | 74 |
29. exp research design/ | 134,468 |
30. 28 and 29 | 15 |
31. 1 and 16 | 547 |
32. ep.fs. | 434,923 |
33. exp epidemiology/ | 6,500 |
34. 32 or 33 | 437,784 |
35. 31 and 34 | 29 |
36. exp incidence/ | 81,260 |
37. exp prevalence/ | 83,713 |
38. 36 or 37 | 157,239 |
39. 31 and 38 | 14 |
40. 26 or 30 or 35 or 39 | 268 |
41. limit 40 to english language | 267 |
42. limit 41 to journal article | 251 |
43. from 42 keep 1-251 | 251 |
MEDLINE search via PubMed | |
("Biomedical Research/methods"[MeSH] OR "Biomedical Research/organization and administration"[MeSH] OR "Biomedical Research/standards"[MeSH] OR "Biomedical Research/statistics and numerical data"[MeSH] OR "Biomedical Research/trends"[MeSH]) Limits: Humans, Journal Article, English | 3,703 |
"Epidemiologic Studies"[MeSH] AND "Research Design/standards"[MeSH] AND ("Evaluation Studies as Topic/classification"[MeSH] OR "Evaluation Studies as Topic/methods"[MeSH] OR "Evaluation Studies as Topic/standards"[MeSH]) Limits: Humans, Journal Article, English | 59 |
"Publishing/standards"[MeSH] AND "Epidemiologic Methods"[MeSH] AND "Research Design/standards"[MeSH] Limits: Humans, Journal Article, English | 65 |
"STROBE Initiative"[Corporate Author] | 10 |
"Bias (Epidemiology)"[MeSH] AND "Epidemiologic Studies"[MeSH] AND "Epidemiologic Methods"[MeSH] AND "Research Design/standards"[MeSH] Limits: Humans, Journal Article, English | 97 |
"Evidence-Based Medicine"[MeSH] AND "Epidemiologic Studies"[MeSH] AND "Epidemiologic Methods"[MeSH] AND "Research Design/standards"[MeSH] Limits: Humans, Journal Article, English | 25 |
"Research Design/standards"[MeSH] AND "Epidemiologic Studies"[MeSH] AND "Epidemiologic Measurements"[MeSH] AND "Bias (Epidemiology)"[MeSH] Limits: Humans, Journal Article, English AND "Incidence"[MeSH] Limits: Humans, Journal Article, English | 8 |
"Research Design/standards"[MeSH] AND "Epidemiologic Studies"[MeSH] AND "Epidemiologic Measurements"[MeSH] AND "Bias (Epidemiology)"[MeSH] Limits: Humans, Journal Article, English AND "Prevalence"[MeSH] Limits: Humans, Journal Article, English | 7 |
("Prevalence"[MeSH]) AND systematic[sb] "Working group" Limits: English | 15 |
[CN] Limits: Humans, Meta-Analysis, English, Core clinical journals | 2 |
("Prevalence"[MeSH]) AND systematic[sb] Limits: Humans, Meta-Analysis, English, Core clinical journals | 83 |
Moher D[author] | 198 |
"Epidemiologic Studies"[MeSH] Limits: Humans, Meta-Analysis, English AND "Incidence"[MeSH] Limits: Humans, Meta-Analysis, English Limits: Humans, Meta-Analysis, English, Core clinical journals | 57 |
"Epidemiologic Studies"[MeSH] AND "Incidence"[MeSH] Limits: Humans, Meta-Analysis, English | 236 |
"Epidemiologic Studies"[MeSH] AND "Incidence"[MeSH] AND Evidence Limits: Humans, Meta-Analysis, English | 52 |
"Incidence"[MeSH] Limits: Humans, Meta-Analysis, English | 635 |
"Risk"[MeSH] AND "Epidemiologic Studies"[MeSH] Limits: Humans, Meta-Analysis, English, Core clinical journals | 273 |
"Prevalence"[MeSH] Limits: Humans, Meta-Analysis, English, Core clinical journals | 84 |
Altman DG[author] | 7 |
Higgins J[author] | 3 |
"Review Literature as Topic"[MeSH] AND "Research Design/standards"[MeSH] AND "Epidemiologic Studies"[MeSH] Limits: Humans, English, Core clinical journals | 0 |
"Review Literature as Topic"[MeSH] AND "Epidemiologic Studies"[MeSH] AND "Quality control"[MeSH] | 1 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] | 0 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND ("Data Collection/methods"[MeSH] OR "Data Collection/standards"[MeSH]) | 5 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Bias (Epidemiology)"[MeSH] | 1 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND ("Questionnaires/methods"[MeSH] OR "Questionnaires/standards"[MeSH]) | 0 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Evidence-Based Medicine"[MeSH] | 2 |
"Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Reproducibility of Results"[MeSH] | 3 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] | 0 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND ("Data Collection/methods"[MeSH] OR "Data Collection/standards"[MeSH]) | 16 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Bias (Epidemiology)"[MeSH] | 6 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND ("Questionnaires/methods"[MeSH] OR "Questionnaires/standards"[MeSH]) | 1 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Evidence-Based Medicine"[MeSH] | 0 |
"Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Reproducibility of Results"[MeSH] | 12 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] | 0 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Research Design/standards"[MeSH] | 1 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND ("Data Collection/methods"[MeSH] OR "Data Collection/standards"[MeSH]) | 18 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Bias (Epidemiology)"[MeSH] | 7 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND ("Questionnaires/methods"[MeSH] OR "Questionnaires/standards"[MeSH]) | 1 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Evidence-Based Medicine"[MeSH] | 4 |
"Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Reproducibility of Results"[MeSH] | 10 |
"Health Care Quality, Access, and Evaluation"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Health Care Quality, Access, and Evaluation"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Peer Review, Research"[MeSH] | 0 |
"Health Care Quality, Access, and Evaluation"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Research Design/standards"[MeSH] | 4 |
"Health Care Quality, Access, and Evaluation"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Evidence-Based Medicine"[MeSH] | 8 |
"Health Care Quality, Access, and Evaluation"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Bias (Epidemiology)"[MeSH] | 33 |
"Models, Statistical"[MeSH] AND "Risk Factors"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Models, Statistical"[MeSH] AND "Incidence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Models, Statistical"[MeSH] AND "Prevalence"[MeSH] AND "Chronic Disease/epidemiology"[MeSH] AND "Research Design/standards"[MeSH] | 0 |
"Epidemiologic Studies"[MeSH] AND "Models, Statistical"[MeSH] AND "Research Design/standards"[MeSH] | 47 |
"Prevalence"[MeSH] AND "Epidemiologic Studies"[MeSH] AND "Models, Statistical"[MeSH] AND "Bias (Epidemiology)"[MeSH] | 61 |
"Incidence"[MeSH] AND "Epidemiologic Studies"[MeSH] AND "Models, Statistical"[MeSH] AND "Bias (Epidemiology)"[MeSH] | 66 |
"Research Design/standards"[MeSH] AND ("Biomedical Research/methods"[MeSH] OR "Biomedical Research/organization and administration"[MeSH] OR "Biomedical Research/standards"[MeSH] OR "Biomedical Research/statistics and numerical data"[MeSH] OR "Biomedical Research/trends"[MeSH]) Limits: Humans, Journal Article, English | 62 |
Abbreviations: MeSH, Medical Subject Heading term; sb, subset; CN, corporate author.
Figure 1.
Study flow to identify systematic reviews of observational studies, scales, and checklists for planned formal internal quality evaluation, and studies about bias in observational research, 1990 through June 2008.
This flow chart shows 3 boxes. The top box reads |
Total references — 1,053 |
|
It is connected by a vertical line to 2 additional boxes. The left box reads |
Included studies — 397 |
|
The right box reads |
Excluded studies — 656 |
|
Table 2.
Publication Characteristics | Outcome | Estimate | Assessment of Quality of Included Studies |
---|---|---|---|
Bracken, 1990 (32)
Country: United States Journal: Obstet Gynecol Sponsorship: Not reported Conflict of interest (COI): Not reported Sponsor participation in data analyses: Not reported |
Congenital malformations in offspring | Risk | No |
Romieu et al, 1990 (33)
Country: United States Journal: Cancer Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Breast cancer | Risk | Quality criteria abstracted |
Haughey et al, 1992 (34)
Country: United States Journal: Ann Otol Rhinol Laryngol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Second malignant tumors in head and neck cancer | Risk | No |
Lemon et al, 1992 (35)
Country: United States Journal: Cancer Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Nonfamilial breast cancer | Continuous variable | No |
McKenna, 1992 (36)
Country: United Kingdom Journal: Am J Med Sponsorship: Nonprofit organization, nursing home COI: Not reported Sponsor participation in data analyses: Not reported |
Differences in vitamin D status | Prevalence | Quality criteria abstracted |
Morris et al, 1992 (37)
Country: United States Journal: Am J Public Health Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Cancer | Risk | Yes |
Myers and Basinski, 1992 (38)
Country: Canada Journal: Arch Intern Med Sponsorship: Nonprofit organization, award COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | No |
Becker et al, 1993 (39)
Country: United States Journal: Ann Emerg Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Survival of cardiac arrest | Risk | No |
Brownson et al, 1993 (40)
Country: United States Journal: Arch Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Adult leukemia | Risk | Yes |
Ernst and Resch, 1993 (41)
Country: Austria Journal: Ann Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Cardiovascular risk factor | Risk | No |
Katerndahl, 1993 (42)
Country: United States Journal: J Nerv Ment Dis Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Panic disorder and mitral valve prolapse | Risk | Yes |
Harris and Barraclough, 1994 (43)
Country: United Kingdom Journal: Medicine Sponsorship: Industry COI: Not reported Sponsor participation in data analyses: Not reported |
Suicide | Risk | No |
Kawachi et al, 1994 (44)
Country: United States Journal: Br Heart J Sponsorship: Industry, scholarship COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | No |
Law et al, 1994 (45)
Country: United Kingdom Journal: BMJ Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Hazards of reducing serum cholesterol | Risk | No |
Law et al, 1994 (46)
Country: United Kingdom Journal: BMJ Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Ischemic heart disease | Risk | No |
Steffen et al, 1994 (47)
Country: Switzerland Journal: JAMA Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Hepatitis A | Risk | No |
Zhang and Begg, 1994 (48)
Country: United States Journal: Int J Epidemiol Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Cervical neoplasia | Risk | No |
Everhart and Wright, 1995 (49)
Country: United States Journal: JAMA Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Pancreatic cancer | Risk | No |
Feinberg et al, 1995 (50)
Country: United States Journal: Arch Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Atrial fibrillation | Prevalence | No |
Ritchie and Kildea, 1995 (51)
Country: France Journal: Lancet Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Senile dementia | Prevalence | No |
Raman-Wilms et al, 1995 (52)
Country: Canada Journal: Obstet Gynecol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Fetal genital effects | Risk | No |
Hatsukami and Fischman, 1996 (53)
Country: United States Journal: JAMA Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Use of crack cocaine and cocaine hydrochloride | Prevalence | No |
Hill and Schoener, 1996 (54)
Country: United States Journal: Am J Psychiatry Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Attention deficit hyperactivity disorder | Prevalence | No |
Hackshaw et al, 1997 (55)
Country: United Kingdom Journal: BMJ Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The views expressed are those of the authors and not necessarily those of the Department of Health." |
Lung cancer | Risk | No |
Kluijtmans et al, 1997 (56)
Country: Netherlands Journal: Circulation Sponsorship: Nonprofit organization, industry COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary artery disease | Risk | No |
Law and Hackshaw, 1997 (57)
Country: United Kingdom Journal: BMJ Sponsorship: None COI: Reported as not a conflict of interest Sponsor participation in data analyses: None |
Hip fracture | Risk | No |
Law et al, 1997 (58)
Country: United Kingdom Journal: BMJ Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The Department of Health (England) supported this work, although the views are our own." |
Ischemic heart disease | Risk | No |
Danesh et al, 1998 (59)
Country: United Kingdom Journal: JAMA Sponsorship: Scholarship, nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | Yes |
French and Brocklehurst, 1998 (60)
Country: United Kingdom Journal: Br J Obstet Gynaecol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Survival in women infected with human immunodeficiency virus | Risk | Yes |
Forgie et al, 1998 (61)
Country: Canada Journal: Arch Intern Med Sponsorship: Industry, government, fellowships, nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Allogeneic blood transfusion | Risk | No |
Huang et al, 1998 (62)
Country: Canada Journal: Gastroenterology Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Gastric cancer | Risk | Yes |
Johnston et al, 1998 (63)
Country: United States Journal: Neurology Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Subarachnoid hemorrhage | Risk | No |
Lazarou et al, 1998 (64)
Country: Canada Journal: JAMA Sponsorship: Scholarship, nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Adverse drug reactions in hospitalized patients | Prevalence | Quality criteria abstracted |
Ray, 1998 (65)
Country: Canada Journal: Arch Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Venous thromboembolic disease | Risk | Quality criteria abstracted |
Spencer-Green, 1998 (66)
Country: United States Journal: Arch Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Secondary diseases from primary Reynaud phenomenon | Risk | Yes |
Stratton et al, 1998 (67)
Country: United Kingdom Journal: Br J Obstet Gynaecol Sponsorship: Research fellowship, nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Ovarian cancer | Risk | No |
Zock and Katan, 1998 (68)
Country: Netherlands Journal: Am J Clin Nutr Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Breast, colorectal, and prostate cancer | Risk | Quality criteria abstracted |
Zondervan et al, 1998 (69)
Country: United Kingdom Journal: Br J Obstet Gynaecol Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Chronic pelvic pain in women | Prevalence | No |
Angelillo and Villari, 1999 (70)
Country: Italy Journal: Bull World Health Organ Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Childhood leukemia | Risk | Yes |
He et al, 1999 (71)
Country: United States Journal: N Engl J Med Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | No |
Shaffer et al, 1999 (72)
Country: United States Journal: Am J Public Health Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Disordered gambling behavior | Prevalence | No |
Wittrup et al, 1999 (73)
Country: Denmark Journal: Circulation Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Ischemic heart disease | Risk | Yes |
Yoder et al, 1999 (74)
Country: United States Journal: Obstet Gynecol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Fetus with isolated choroid plexus cysts | Risk | No |
Christen et al, 2000 (75)
Country: United States Journal: Arch Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Cardiovascular disease | Risk | Yes |
Cleophas et al, 2000 (76)
Country: Netherlands Journal: Am J Cardiol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary artery disease | Risk | Yes |
DiMatteo et al, 2000 (77)
Country: United States Journal: Arch Intern Med Sponsorship: Industry, scholarship COI: Not reported Sponsor participation in data analyses: Not reported |
Noncompliance with medical treatment | Risk | Quality criteria abstracted |
WHO Collaborative Study Team on the Role of Breastfeeding on the Prevention of Infant Mortality, 2000 (78)
Country: Brazil Journal: Lancet Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Infant and child mortality | Risk | No |
Wilson et al, 2000 (79)
Country: Canada Journal: Arch Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Mortality after myocardial infarction | Risk | Yes |
Zeegers et al, 2000 (80)
Country: Netherlands Journal: Cancer Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Urinary tract cancer | Risk | Yes |
Danesh et al, 2001 (81)
Country: United Kingdom Journal: Circulation Sponsorship: Government, scholarship COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | No |
Eaden et al, 2001 (82)
Country: United Kingdom Journal: Gut Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Colorectal cancer | Risk | Yes |
Faraone et al, 2001 (83)
Country: United States Journal: Am J Psychiatry Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Attention deficit hyperactivity disorder | Risk | Yes |
Horta et al, 2001 (84)
Country: Brazil Journal: Am J Public Health Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Early weaning | Risk | Yes |
Rebora, 2001 (85)
Country: Italy Journal: Arch Dermatol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary artery disease | Risk | Yes |
Cannon et al, 2002 (86)
Country: United Kingdom Journal: Am J Psychiatry Sponsorship: Research fellowship, nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Schizophrenia | Risk | No |
Hellermann et al, 2002 (87)
Country: United States Journal: Am J Med Sponsorship: Government, nonprofit organization, fellowship COI: Not reported Sponsor participation in data analyses: Not reported |
Heart failure | Risk | No |
Huang et al, 2002 (88)
Country: Canada Journal: Lancet Sponsorship: Not reported COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Peptic-ulcer disease | Risk | Yes |
Huncharek et al, 2002 (89)
Country: United States Journal: Am J Public Health Sponsorship: Nonprofit organization, industry COI: Not reported Sponsor participation in data analyses: Not reported |
Malignant melanoma | Risk | Yes |
Juul et al, 2002 (90)
Country: Denmark Journal: Blood Sponsorship: Government, nonprofit organization COI: Not reported Sponsor participation in data analyses: "They had no role in gathering, analyzing, or interpreting the data and had no right to approve or disapprove the submitted paper." |
Factor V Leiden | Risk | Yes |
Kelly et al, 2002 (91)
Country: United States Journal: Neurology Sponsorship: Nonprofit organization, industry, fellowship COI: Not reported Sponsor participation in data analyses: Not reported |
Risk of ischemic stroke | Risk | No |
Klerk et al, 2002 (92)
Country: Netherlands Journal: JAMA Sponsorship: Government, "public/private partnership" COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | Yes |
Kozer et al, 2002 (93)
Country: Canada Journal: Am J Obstet Gynecol Sponsorship: Industry COI: Not reported Sponsor participation in data analyses: Not reported |
Congenital anomalies | Risk | No |
Law et al, 2002 (94)
Country: United Kingdom Journal: Arch Intern Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Death after myocardial infarction | Risk | No |
Wald et al, 2002 (95)
Country: United Kingdom Journal: BMJ Sponsorship: None COI: Reported as not a conflict of interest Sponsor participation in data analyses: None |
Cardiovascular disease | Risk | No |
Wald and Link, 2002 (96)
Country: United States Journal: J Infect Dis Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Human immunodeficiency virus infection | Risk | No |
Benjamin et al, 2003 (97)
Country: United States Journal: Pediatrics Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
End-organ damage | Prevalence | No |
Clarfield, 2003 (98)
Country: Israel Journal: Arch Intern Med Sponsorship: Not reported COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Reversible dementias | Prevalence | No |
Cole and Dendukuri, 2003 (99)
Country: Canada Journal: Am J Psychiatry Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Depression among elderly community subjects | Risk | Yes |
Gisbert et al, 2003 (100)
Country: Spain Journal: Gastroenterology Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Hepatitis C virus infection | Risk | Yes |
Glatt et al, 2003 (101)
Country: United States Journal: Am J Psychiatry Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Schizophrenia | Risk | No |
Halbert et al, 2003 (102)
Country: United States Journal: Chest Sponsorship: Industry COI: Not reported Sponsor participation in data analyses: Not reported |
Prevalence estimates for chronic obstructive pulmonary disease | Prevalence | No |
Huang et al, 2003 (103)
Country: Canada Journal: Gastroenterology Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Gastric cancer | Risk | Yes |
Rey et al, 2003 (104)
Country: Canada Journal: Lancet Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Fetal loss | Risk | Yes |
Riboli and Norat, 2003 (105)
Country: France Journal: Am J Clin Nutr Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Cancer risk | Risk | No |
Scholten-Peeters et al, 2003 (106)
Country: Netherlands Journal: Pain Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Whiplash-associated disorders | Risk | Yes |
Thurnham et al, 2003 (107)
Country: United Kingdom Journal: Lancet Sponsorship: Government, fellowship COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The funding source had no role in study design, data collection, data analysis, data interpretation, or in the writing of this report." |
Vitamin A deficiency | Continuous variable | No |
Zeegers et al, 2003 (108)
Country: Netherlands Journal: Cancer Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Prostate carcinoma | Risk | No |
Burzotta et al, 2004 (109)
Country: Italy Journal: Heart Sponsorship: Fellowship COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary ischemic syndromes | Risk | No |
Casas et al, 2004 (110)
Country: United Kingdom Journal: Circulation Sponsorship: Government, 1 author holds a chair of nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Ischemic heart disease | Risk | No |
Casas et al, 2004 (111)
Country: United Kingdom Journal: Arch Neurol Sponsorship: Fellowship COI: Not reported Sponsor participation in data analyses: Not reported |
Ischemic stroke | Risk | No |
He et al, 2004 (112)
Country: United States Journal: Circulation Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease mortality | Risk | No |
Huang et al, 2004 (113)
Country: United States Journal: Neurology Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Sporadic Parkinson disease | Risk | No |
Klement et al, 2004 (114)
Country: Israel Journal: Am J Clin Nutr Sponsorship: Medical center COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Inflammatory bowel disease | Risk | Yes |
Kovalevsky et al, 2004 (115)
Country: United States Journal: Arch Intern Med Sponsorship: Not reported COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Recurrent pregnancy loss | Risk | No |
Levitan et al, 2004 (116)
Country: United States Journal: Arch Intern Med Sponsorship: Not reported COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Cardiovascular disease | Risk | No |
Lovett et al, 2004 (117)
Country: United Kingdom Journal: Neurology Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Subtype of ischemic stroke | Risk | Yes |
Mitsikostas et al, 2004 (118)
Country: Greece Journal: Brain Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Headache | Risk | No |
Montanez et al, 2004 (119)
Country: United States Journal: Arch Intern Med Sponsorship: Not reported COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Total and cardiovascular mortality and sudden death | Risk | No |
Woodbury and Houghton, 2004 (120)
Country: Canada Journal: Ostomy Wound Manage Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Pressure ulcers | Prevalence | Yes |
Bolland et al, 2005 (121)
Country: New Zealand Journal: J Clin Endocrinol Metab Sponsorship: Scholarship COI: Not reported Sponsor participation in data analyses: Not reported |
Increased body weight | Risk | Quality criteria abstracted |
Contopoulos-Ioannidis et al, 2005 (122)
Country: Greece Journal: J Allergy Clin Immunol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Asthma phenotypes | Risk | Quality criteria abstracted |
Dauchet et al, 2005 (123)
Country: France Journal: Neurology Sponsorship: Nonprofit organization, educational institute COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Stroke | Risk | No |
Etminan et al, 2005 (124)
Country: Canada Journal: BMJ Sponsorship: Government, fellowship COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Ischemic stroke | Risk | Yes |
Fazel et al, 2005 (125)
Country: United Kingdom Journal: Lancet Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The sponsors of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication." |
Serious mental disorder | Prevalence | Quality criteria abstracted |
García-Closas et al, 2005 (126)
Country: United States Journal: Lancet Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The study sponsors had no role in the design of the study; in the collection, analysis, or interpretation of the data; or in the writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit the paper for publication." |
Bladder cancer | Risk | No |
Lee et al, 2005 (127)
Country: United States Journal: Arthritis Rheum Sponsorship: Government, industry COI: Not reported Sponsor participation in data analyses: Unrestricted |
Systemic lupus erythematosus | Risk | No |
Lin and August, 2005 (128)
Country: United States Journal: Obstet Gynecol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Preeclampsia | Risk | No |
McDonald et al, 2005 (129)
Country: Canada Journal: Am J Obstet Gynecol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Perinatal outcomes | Risk | Yes |
Palmer, 2005 (130)
Country: United States Journal: Arch Gen Psychiatry Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Lifetime risk of suicide in schizophrenia | Prevalence | Quality criteria abstracted |
Sin et al, 2005 (131)
Country: Canada Journal: Chest Sponsorship: Nonprofit organization, educational institute COI: Not reported Sponsor participation in data analyses: Not reported |
Cardiovascular mortality | Risk | Yes |
Boudville et al, 2006 (132)
Country: Canada Journal: Ann Intern Med Sponsorship: Government, fellowship COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The study sponsors had no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the paper for publication." |
Hypertension | Risk | No |
Clark et al, 2006 (133)
Country: United Kingdom Journal: Pediatrics Sponsorship: Fellowship COI: Not reported Sponsor participation in data analyses: Not reported |
Fractures | Risk | Yes |
de Boer et al, 2006 (134)
Country: Netherlands Journal: Cancer Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Unemployment | Risk | Yes |
Di Castelnuovo et al, 2006 (135)
Country: Italy Journal: Arch Intern Med Sponsorship: Government COI: Not reported Sponsor participation in data analyses: "The sponsor of the study had no involvement in study design; data collection, analysis, or interpretation; writing of the report; or in the decision to submit the paper for publication." |
Total mortality in men and women | Risk | Yes |
Flores-Mateo et al, 2006 (136)
Country: United States Journal: Am J Clin Nutr Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | Yes |
Galassi et al, 2006 (137)
Country: United States Journal: Am J Med Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Cardiovascular disease | Risk | Quality criteria abstracted |
Huxley et al, 2006 (138)
Country: Australia Journal: BMJ Sponsorship: Government, fellowship, industry COI: Reported as not a conflict of interest Sponsor participation in data analyses: Unconditional |
Fatal coronary heart disease | Risk | Quality criteria abstracted |
Kahlenborn et al, 2006 (139)
Country: United States Journal: Mayo Clin Proc Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Premenopausal breast cancer | Risk | Quality criteria abstracted |
Larsson et al, 2006 (140)
Country: Sweden Journal: Gastroenterology Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Esophageal, gastric, and pancreatic cancer | Risk | Quality criteria abstracted |
Mahid et al, 2006 (141)
Country: United States Journal: Mayo Clin Proc Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: Not reported |
Inflammatory bowel disease | Risk | Yes |
Owen et al, 2006 (142)
Country: United Kingdom Journal: Am J Clin Nutr Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Type 2 diabetes | Risk | Quality criteria abstracted |
Ownby et al, 2006 (143)
Country: United States Journal: Arch Gen Psychiatry Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Alzheimer disease | Risk | Yes |
Pavia et al, 2006 (144)
Country: Italy Journal: Am J Clin Nutr Sponsorship: Not reported COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Oral cancer | Risk | Yes |
Riddle et al, 2006 (145)
Country: United States Journal: Am J Trop Med Hyg Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Diarrhea | Prevalence | Yes |
Rutledge et al, 2006 (146)
Country: United States Journal: J Am Coll Cardiol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Depression | Prevalence/ risk | Quality criteria abstracted |
Smith et al, 2006 (147)
Country: United States Journal: J Am Coll Cardiol Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Renal impairment | Risk | Yes |
Weis et al, 2006 (148)
Country: United States Journal: Arch Ophthalmol Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Uveal melanoma | Risk | Quality criteria abstracted |
Williams et al, 2006 (149)
Country: United Kingdom Journal: Arch Dis Child Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Autism spectrum disorders | Prevalence/ risk | Quality criteria abstracted |
Bahekar et al, 2007 (150)
Country: United States Journal: Am Heart J Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Coronary heart disease | Risk | Yes |
Baurecht et al, 2007 (151)
Country: Germany Journal: J Allergy Clin Immunol Sponsorship: Government, university COI: Reported as a conflict of interest Sponsor participation in data analyses: Not reported |
Atopic eczema | Risk | No |
Bellamy et al, 2007 (152)
Country: United Kingdom Journal: BMJ Sponsorship: Government, fellowship COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Cardiovascular disease | Risk | Quality criteria abstracted |
Conde-Agudelo et al, 2007 (153)
Country: Colombia Journal: Am J Obstet Gynecol Sponsorship: Government COI: Not reported Sponsor participation in data analyses: "The content of the paper has not been influenced by the sponsor." |
Maternal health | Risk | Yes |
Dehghan et al, 2007 (154)
Country: Netherlands Journal: Diabetes Sponsorship: University, government COI: Not reported Sponsor participation in data analyses: Not reported |
Diabetes | Risk | No |
Eichler et al, 2007 (155)
Country: Switzerland Journal: Am Heart J Sponsorship: Nonprofit organization COI: Not reported Sponsor participation in data analyses: "The funding source had no influence on study design; in the collection, analysis, and interpretation of the data; in the writing of the manuscript; and in the decision to submit the manuscript for publication." |
First coronary events | Risk | Yes |
Gami et al, 2007 (156)
Country: United States Journal: J Am Coll Cardiol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Cardiovascular events and death | Risk | Yes |
Grulich et al, 2007 (157)
Country: Australia Journal: Lancet Sponsorship: Government, fellowship, scholarship COI: Reported as a conflict of interest Sponsor participation in data analyses: "There was no funding source for this study. All authors had access to all the data. The corresponding author had final responsibility for the decision to submit for publication." |
Cancers | Risk | Yes |
Havemann et al, 2007 (158)
Country: United States Journal: Gut Sponsorship: Industry COI: Reported as a conflict of interest Sponsor participation in data analyses: Not reported |
Asthma | Risk | Quality criteria abstracted |
Hirtz et al, 2007 (159)
Country: United States Journal: Neurology Sponsorship: Not reported COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Common neurologic disorders | Prevalence | Yes |
Huxley et al, 2007 (160)
Country: Australia Journal: Am J Clin Nutr Sponsorship: Government, nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: "None of the funding sources had any role in the study design, data analysis, data interpretation, writing of the paper, or the decision to submit the paper for publication." |
Ischemic heart disease | Risk | Yes |
Krishna and Kim, 2007 (161)
Country: United States Journal: J Neurosurg Sponsorship: Government COI: Not reported Sponsor participation in data analyses: Not reported |
Risk factors for subarachnoid hemorrhage | Risk | Quality criteria abstracted |
Langan et al, 2007 (162)
Country: United Kingdom Journal: Arch Dermatol Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The sponsor had no role in the design and conduct of the study; in the collection, analysis, and interpretation of data; or in the preparation, review, or approval of the manuscript." |
Eczema | Risk | Quality criteria abstracted |
Larsson and Wolk, 2007 (163)
Country: Sweden Journal: Am J Clin Nutr Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Colon and rectal cancer risk | Risk | Quality criteria abstracted |
Larsson and Wolk, 2007 (164)
Country: Sweden Journal: Gastroenterology Sponsorship: Nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: "The sponsor had no role in the study design or in the collection, analysis, and interpretation of the data." |
Liver cancer | Risk | Quality criteria abstracted |
Liu et al, 2007 (165)
Country: China Journal: J Am Coll Cardiol Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Recurrence of atrial fibrillation after successful electrical cardioversion | Risk | Yes |
Loza and Chang, 2007 (166)
Country: United States Journal: J Allergy Clin Immunol Sponsorship: Government, nonprofit organization COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Atopic asthma risk | Risk | Yes |
Pittas et al, 2007 (167)
Country: United States Journal: J Clin Endocrinol Metab Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Type 2 diabetes | Risk | No |
Polanczyk et al, 2007 (168)
Country: Brazil Journal: Am J Psychiatry Sponsorship: Industry, foreign grants COI: Not reported Sponsor participation in data analyses: "There was no involvement of any funding source in the study design, data collection, analysis, interpretation of data, and writing of this article or in the decision to submit the article for publication." |
Attention deficit hyperactivity disorder | Prevalence | No |
Rona et al, 2007 (169)
Country: United Kingdom Journal: J Allergy Clin Immunol Sponsorship: Government COI: Reported as a conflict of interest Sponsor participation in data analyses: Not reported |
Food allergy | Prevalence | Quality criteria abstracted |
Sarwar et al, 2007 (170)
Country: United Kingdom Journal: Circulation Sponsorship: Government, scholarship, industry COI: Reported as not a conflict of interest Sponsor participation in data analyses: Unrestricted |
Coronary heart disease | Risk | No |
Snoep et al, 2007 (171)
Country: Netherlands Journal: Am Heart J Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Clopidogrel nonresponsiveness | Prevalence | Yes |
Zintzaras and Kaditis, 2007 (172)
Country: Greece Journal: Arch Pediatr Adolesc Med Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Blood pressure | Risk | Yes |
Ageno et al, 2008 (173)
Country: Italy Journal: Circulation Sponsorship: Not reported COI: Not reported Sponsor participation in data analyses: Not reported |
Venous thromboembolism | Risk | Yes |
Barclay et al, 2008 (174)
Country: Australia Journal: Am J Clin Nutr Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Chronic disease risk | Risk | Quality criteria abstracted |
Conde-Agudelo et al, 2008 (175)
Country: United States Journal: Am J Obstet Gynecol Sponsorship: Government COI: Not reported Sponsor participation in data analyses: "The views expressed in this document are solely the responsibility of the authors and do not necessarily represent the views of the World Health Organization." |
Risk of preeclampsia | Risk | Yes |
Schunkert et al, 2008 (176)
Country: Germany Journal: Circulation Sponsorship: Government COI: Reported as not a conflict of interest Sponsor participation in data analyses: Not reported |
Coronary artery disease | Risk | No |
Footnotes
The opinions expressed by authors contributing to this journal do not necessarily reflect the opinions of the US Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above. URLs for nonfederal organizations are provided solely as a service to our users. URLs do not constitute an endorsement of any organization by CDC or the federal government, and none should be inferred. CDC is not responsible for the content of Web pages found at these URLs.
Suggested citation for this article: Shamliyan T, Kane RL, Jansen S. Quality of systematic reviews of observational nontherapeutic studies. Prev Chronic Dis 2010;7(6) http://www.cdc.gov/pcd/issues/2010/nov/09_0195.htm. Accessed [date].
Contributor Information
Tatyana Shamliyan, Minnesota Evidence-based Practice Center, University of Minnesota School of Public Health; D351 Mayo (MMC 197), 420 Delaware St SE, Minneapolis, MN 55455, Phone: 612-624-1185, Email: shaml005@umn.edu.
Robert L. Kane, University of Minnesota School of Public Health, Minneapolis, Minnesota.
Stacy Jansen, University of Minnesota School of Public Health, Minneapolis, Minnesota.
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