Table 3:

Sensitivity and subgroup analyses

ComparisonNo. of trialsI2Difference* between SMDs (95% CI)
%p value
Main analysis16460.02−0.23 (−0.40 to −0.06)
Type of analysis
SMD standardized by SD of blinded control group16530.007−0.26 (−0.44 to −0.08)
SMD standardized separately for blinded and nonblinded assessors16470.02−0.23 (−0.40 to −0.06)
Correlation accounted for by correlation coefficient788< 0.001−0.36 (−0.64 to −0.08)
Correlation accounted for by correlation coefficient or median correlation coefficient1678< 0.001−0.21 (−0.35 to −0.07)
Increased precision in crossover/split-body trials was accounted for16470.02−0.22 (−0.39 to −0.06)
All trials given same weight16NA−0.21 (NA)
Type of data
Individual patient data1NA−0.16 (−0.65 to 0.34)
Correlation data with no individual patient data6600.03−0.46 (−0.83 to −0.10)
Basic outcome data with no information on correlation90> 0.9−0.06 (−0.20 to 0.07)
Clinical condition
Facial wrinkles388< 0.001−0.39 (−1.03 to 0.25)
Angina pectoris200.7−0.56 (−0.90 to −0.23)
Parkinson disease200.7−0.17 (−0.49 to 0.15)
Other90> 0.9−0.06 (−0.21 to 0.10)
Trial characteristics
Nonblind assessment by multiple observer consensus1NA0.14 (−0.65 to 0.94)
Nonblind assessment by single observer15490.02−0.25 (−0.42 to −0.07)
Publication status: observer bias main objective400.8−0.07 (−0.41 to 0.28)
Publication status: observer bias not main objective12580.01−0.27 (−0.47 to −0.06)
Design: parallel group13560.01−0.27 (−0.49 to −0.06)
Design: crossover/split-body30> 0.9−0.08 (−0.35 to 0.20)
Funding: industry10660.002−0.28 (−0.52 to −0.04)
Funding: noncommercial or unclear source600.9−0.13 (−0.38 to 0.12)
Risk of confounding
Timing of blind and nonblind assessment: same/similar16460.02−0.23 (−0.40 to −0.06)
Timing of blind and nonblind assessment: not same/similar0NANA
Assessors: same type (e.g., neurologists v. neurologists)1000.6−0.13 (−0.27 to 0.01)
Assessors: not same (e.g., neurologists v. physiotherapists)6730.002−0.30 (−0.69 to 0.09)
Procedure: same type (e.g., clinical exam v. clinical exam)600.9−0.09 (−0.24 to 0.06)
Procedure: not same type (e.g., clinical exam v. video of clinical exam)10600.008−0.30 (−0.57 to −0.02)
Blinding procedures: probably effective11500.03−0.19 (−0.44 to 0.06)
Blinding procedures: possibly not effective5480.1−0.28 (−0.54 to −0.02)
Patients: all seen by both blinded and nonblinded assessors600.5−0.29 (−0.49 to −0.09)
Patients: a minority seen only by one type of assessor10590.009−0.20 (−0.46 to 0.06)
  • Note: CI = confidence interval, NA = not available, SD = standard deviation, SMD = standardized mean difference.

  • * Pooled difference between SMD based on blind assessments and the corresponding SMD based nonblind assessments. dSMD < 0 suggests than nonblind assessors provide more optimistic estimates of the intervention’s effect.

  • Seven trials reported a correlation coefficient between blind and nonblind assessments. We used the median correlation coefficient as a correction factor in the 9 trials without such information.

  • Crossover/split-body trials were assigned more weight when their standard error was calculated based on the paired difference (in our planned main analysis, all studies were handled as parallel group trials).