Table S1.
Downs and Black 27-item Checklist
| Checklist question | Scoring | |
|---|---|---|
| Reporting | 1) Is the hypothesis/aim/objective of the study clearly described? | Yes = 1; No = 0 |
| 2) Are the main outcomes to be measured clearly described in the introduction or methods section? | Yes = 1; No = 0 | |
| 3) Are the characteristics of the patients included in the study clearly described? | Yes = 1; No = 0 | |
| 4) Are the interventions of interest clearly described? | Yes = 1; No = 0 | |
| 5) Are the distributions of principal confounders in each group of patients to be compared clearly described? | Yes = 2; Partially = 1; No = 0 | |
| 6) Are the main findings of the study clearly described? | Yes = 1; No = 0 | |
| 7) Does the study provide estimates of the random variability in the data for the main outcomes? | Yes = 1; No = 0 | |
| 8) Have all important adverse events that may be a consequence of the intervention been reported? | Yes = 1; No = 0 | |
| 9) Have the characteristics of patients lost to follow-up been described? | Yes = 1; No = 0 | |
| 10) Have actual probability values been reported (eg, 0.035 rather than <0.05) for the main outcomes, except where the probability value is <0.001? | Yes = 1; No = 0 | |
| External validity | 11) Were the subjects asked to participate in the study representative of the entire population from which they were recruited? | Yes = 1; No = 0; Unable to determine = 0 |
| 12) Were those subjects who were prepared to participate representative of the entire population from which they were recruited? | Yes = 1; No = 0; Unable to determine = 0 | |
| 13) Were the staff, places, and facilities where the patients were treated representative of the treatment the majority of patients receive? | Yes = 1; No = 0; Unable to determine = 0 | |
| Internal validity – bias | 14) Was an attempt made to blind study subjects to the intervention they have received? | Yes = 1; No = 0; Unable to determine = 0 |
| 15) Was an attempt made to blind those measuring the main outcomes of the intervention? | Yes = 1; No = 0; Unable to determine = 0 | |
| 16) If any of the results of the study were based on “data dredging,” was this made clear? | Yes = 1; No = 0; Unable to determine = 0 | |
| 17) In trials and cohort studies, do the analyses adjust for different lengths of follow- up of patients, or in case–control studies, is the time period between the intervention and outcome the same for cases and controls? | Yes = 1; No = 0; Unable to determine = 0 | |
| 18) Were the statistical tests used to assess the main outcomes appropriate? | Yes = 1; No = 0; Unable to determine = 0 | |
| 19) Was compliance with the intervention(s) reliable? | Yes = 1; No = 0; Unable to determine = 0 | |
| 20) Were the main outcome measures used accurate (valid and reliable)? | Yes = 1; No = 0; Unable to determine = 0 | |
| Internal validity – confounding (selection bias) | 21) Were the patients in different intervention groups (trials and cohort studies) or were the cases and controls (case–control studies) recruited from the same population? | Yes = 1; No = 0; Unable to determine = 0 |
| 22) Were study subjects in different intervention groups (trials and cohort studies) or were the cases and controls (case–control studies) recruited over the same period of time? | Yes = 1; No = 0; Unable to determine = 0 | |
| 23) Were study subjects randomized to intervention groups? | Yes = 1; No = 0; Unable to determine = 0 | |
| 24) Was the randomized intervention assignment concealed from both patients and health care staff until recruitment was complete and irrevocable? | Yes = 1; No = 0; Unable to determine = 0 | |
| 25) Was there adequate adjustment for confounding in the analyses from which the main findings were drawn? | Yes = 1; No = 0; Unable to determine = 0 | |
| 26) Were losses of patients to follow-up taken into account? | Yes = 1; No = 0; Unable to determine = 0 | |
| Power | 27) Did the study have sufficient power to detect a clinically important effect where the probability value for a difference being due to chance is less than 5%? | Yes = 1; No = 0; Unable to determine = 0 |
Notes: The Downs and Black Checklist is a 27-item methodological quality assessment tool of randomized and nonrandomized studies of health care interventions. The maximum score is 28 since all individual items were rated as yes (=1), no (=0), or unable to determine (=0), with the exception of Item 5, where a maximum of 2 points could be received. Scores are grouped into four categories: excellent (26–28 points); good (20–25); fair (15–19); and poor (≤14).