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. 2020 Feb 18;14(1):171–179. doi: 10.1055/s-0039-1693507

Table 1. Domains and risk of bias considered in risk of bias evaluation according to Fowkes and Fulton.

Guidelines Checklist Description
Study design appropriate to objectives? Objective common design The type of study was marked in the appropriate type of study. If the type of study was appropriate according to the study design, it was labeled as “0,” and as “++” if it was not appropriate
Prevalence cross-sectional
Prognosis cohort
Treatment controlled trial
Cause cohort, case–control, cross-sectional
Study sample representative? Source of sample The domain was considered “0” in cases of detailed origin, “+” to a specified origin of only one group and “++” in cases of absence of specification of the source of the groups
Sampling method The item was assigned “0” for a full description of sampling method, “+” for poor or no explanation of sample method, with no problem in matching between groups, and “++” for poor or no description of sample method, interfering in the matching of the groups
Sample size A minor problem “+” was considered when the sample was not representative or did not report a sample calculation. To a major problem, “++” was considered when no sample calculation was provided, and the number of participants was less than 50 participants, “0” was considered in the absence of the above factors
Entry criteria/exclusion A minor problem “+” was attributed when the control and case group reported current use of antibiotics or anti-inflammatories, diabetes, smoking or pregnancy. In the case of presence of more than two previously mentioned items, it was considered as a major problem “++”
Nonrespondents The “0” was attributed when there was no refusal to participate in the study, “+” was assigned when there was the refusal, but did not compromise the sample, and “++” when there were refusal and impairment of the sample size
Control group acceptable? Definition of controls It was attributed “0” when all characteristics of the control group were described, “+” when any information was pendent as the origin of the control group, the selection criterions and a different origin between case and control groups and “++” when two or more items described in previously items
Source of controls It was considered “0” when the control group was referred, “+” when the origin of groups was different, but with reasons and “++” when the groups presented different origins without reasons
Matching/randomization In this item, “0” was assigned to cases of randomized/matched groups, “+” to cases of no description of randomization, but with a matching of groups and “++” to no explanation of randomization or matching
Comparable characteristics It was attributed “0” to matched groups or not matched by the impossibility of being subsequently adjusted and “++” the presence of unpaired variables that were not paired or adjusted
Quality of measurements and outcomes? Validity It was considered “0” when the evaluation method applied is appropriate; “+” when using a single method, but with appropriate sensitivity with good specificity; “++” when using a single method, without an adequate specificity or good sensitivity
Reproducibility It was considered “0” whether the evaluation methods were well described; “+” when a lack description of any step of the method was presented, for example, the identification of the patients of the groups studied in laboratory samples, evaluations at different times or application of various methods between groups of individual pathology; “++” when two or more of the previous items are present
Blindness The condition of the study participants was considered to be “Blind,” in this case being assigned the signal “0,” in cases of “not blind” the signal “++” was attributed
Quality control It was considered a problem when the examiner was not qualified; a partial periodontal exam was performed [not in all teeth or not in all the six periodontal sites/teeth], the measurement of periodontitis was only radiographic or the absence of the number of evaluated teeth sites. A minor problem “+” was considered when two of these characteristics were present, and a major problem “++” if more than two of these characteristics were present
Completeness Compliance It was assigned “0” for a sample size that remains the same from the beginning to the end or decreases without compromising the power of the test; “+” for differences in sample size at the end of the study, compromising the power of the test, but with reasons and adjusts; “++” for difference in sample size at the end of the study, compromising the power of the test, without reasons
Dropouts The “0” was scored when there is no loss during the study, “+” when there is a withdrawal that involves the inclusion criteria, such as age, sex, “++” when there is withdrawal and it compromises more than one criterion
Deaths This item was scored as Not Applicable “NA,” due to the type of PECO strategy
Missing data In this item, “0” was assigned to cases of randomized/matched groups, “+” to cases of no description of randomization, but with a matching of groups and “++” to no description of randomization or matching
Distorting influences? Extraneous treatments In this item, “0” was considered when there were no external influences; “+” when there are external influences, but that does not interfere in the results; “++” when there are external influences and interferes with the results
Contamination This item was scored as Not Applicable “NA,” due to the type of PECO strategy
Changes over time In this item, “0” was attributed to data collected in the same period; “+” to data obtained from the control group and the study group at different times that may cause distortions; “++” when the previous item was associated with data from studies already published
Confounding factors A problem was assigned when the data analysis involved enrollment of persons < 5 years. Menopausal woman, smokers, diabetics and obese. A minor problem “+” was assigned when 1 or 2 of these characteristics were present and a major problem “++” if there were 3 or more
Distortion reduced by analysis It was considered “0” when it cites the adjustments of the covariates that present distortions; “+” when the article report adjustment, but does not say the criteria; “++” when distortion was identified, without adjustment
Summary questions Bias: Are the results erroneously biased in a certain direction? YES or “NO” answers were assigned to each question. If the answer is NO to the three questions, the article is considered reliable, with low risk of bias
Confounding: Are there any serious confusing or other distorting influences?
Chance: Is it likely that the results occurred by chance?