Table 4

Critical appraisal of included studies using the Downs and Black checklist

SectionQuestionsAbanobi et al,43  2015Cary et al,42  2016Desouzart et al,17  2016Gordon et al,13 2007
Reporting1Is the hypothesis/aim/objective of the study clearly described?YYYY
2Are the main outcomes to be measured clearly described in the Introduction or Methods section?NYYY
3Are the characteristics of the patients included in the study clearly described?YNYX
4Are the interventions of interest clearly described?XXYX
5Are the distributions of principal confounders in each group of subjects to be compared clearly described?*YX*Y*Y
6Are the main findings of the study clearly described?YYYY
7Does the study provide estimates of the random variability in the data for the main outcomes?YYYY
8Have all important adverse events that may be a consequence of the intervention been reported?XXNX
9Have the characteristics of patients lost to follow-up been described?XXYX
10Have actual probability values been reported (eg, 0.035 rather than<0.05) for the main outcomes except where the probability value is less than 0.001?YYYN
External validity11Were the subjects asked to participate in the study representative of the entire population from which they were recruited?YYNY
12Were those subjects who were prepared to participate representative of the entire population from which they were recruited?UNNN
13Were the staff, places and facilities where the patients were treated, representative of the treatment the majority of patients receive?XXYX
Internal validity: bias14Was an attempt made to blind study subjects to the intervention they have received?XXUX
15Was an attempt made to blind those measuring the main outcomes of the intervention?XXNX
16If any of the results of the study were based on ‘data dredging’, was this made clear?YYYY
17In 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?YXYX
18Were the statistical tests used to assess the main outcomes appropriate?YYYY
19Was compliance with the intervention/s reliable?XXUX
20Were the main outcome measures used accurate (valid and reliable)?YYYY
Internal validity: confounding21Were the patients in different intervention groups (trials and cohort studies) or were the cases and controls (case–control studies) recruited from the same population?YXYY
22Were 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?YXYX
23Were study subjects randomised to intervention groups?XXYX
24Was the randomised intervention assignment concealed from both patients and healthcare staff until recruitment was complete and irrevocable?XXUX
25Was there adequate adjustment for confounding in the analyses from which the main findings were drawn?NNNY
26Were losses of patients to follow-up taken into account?XXYX
Power27Did 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%?NXNN
  • N = no = 0 points, Y = yes = 1 points, *Y = 2 points, U = unable to determine = 0, X = not applicable (see Quality of Evidence section).

  • Evidence levels = strong (>75%), moderate (50%–74%), limited (25%–49%) and poor quality (<24%).47