10.5061/DRYAD.105CB
Holtedahl, Robin
Fram Rehabilitation Centre
Brox, Jens Ivar
Oslo University Hospital
Tjomsland, Ole
South-Eastern Norway Regional Health Authority
Data from: Placebo effects in trials evaluating 12 selected minimally
invasive interventions: a systematic review and meta-analysis
Dryad
dataset
2014
Health economics
Clinical trials
Medical ethics
2014-12-24T15:41:11Z
2014-12-24T15:41:11Z
en
https://doi.org/10.1136/bmjopen-2014-007331
134144 bytes
1
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Objectives: To analyse the impact of placebo effects on outcome in trials
of selected minimally invasive procedures and to assess reported adverse
events in both trial arms. Design: A systematic review and meta-analysis.
Data sources and study selection: We searched MEDLINE and Cochrane library
to identify systematic reviews of musculoskeletal, neurological and
cardiac conditions published between January 2009 and January 2014
comparing selected minimally invasive with placebo (sham) procedures. We
searched MEDLINE for additional randomised controlled trials published
between January 2000 and January 2014. Data synthesis: Effect sizes (ES)
in the active and placebo arms in the trials’ primary and pooled secondary
end points were calculated. Linear regression was used to analyse the
association between end points in the active and sham groups. Reported
adverse events in both trial arms were registered. Results: We included 21
trials involving 2519 adult participants. For primary end points, there
was a large clinical effect (ES≥0.8) after active treatment in 12 trials
and after sham procedures in 11 trials. For secondary end points, 7 and 5
trials showed a large clinical effect. Three trials showed a moderate
difference in ES between active treatment and sham on primary end points
(ES ≥0.5) but no trials reported a large difference. No trials showed
large or moderate differences in ES on pooled secondary end points.
Regression analysis of end points in active treatment and sham arms
estimated an R2 of 0.78 for primary and 0.84 for secondary end points.
Adverse events after sham were in most cases minor and of short duration.
Conclusions: The generally small differences in ES between active
treatment and sham suggest that non-specific mechanisms, including
placebo, are major predictors of the observed effects. Adverse events
related to sham procedures were mainly minor and short-lived. Ethical
arguments frequently raised against sham-controlled trials were generally
not substantiated.
Effect sizesThe spreadsheet includes standard deviations (in some cases
converted from SE or confidence interval) at baseline and at last
follow-up, both in active treatment and sham group in the included 21
trials. Cohen's effect size (standardised mean difference between
baseline and last follow-up) was calculated for primary and pooled
secondary endpoints. The values were adjusted for variable number of
participants (see ref. 14).ES.xls