Abstract
We investigated the influence of indicators of methodological quality on study outcome
in a set of 89 placebo-controlled clinical trials of homoeopathy in three different
ways: (1) The results of studies meeting single criteria (explicit statement of random
allocation, allocation concealment, double-blinding, completeness of follow-up) of
methodological quality were compared with those of studies not meeting the criteria
in univariate and multivariate analyses; (2) The results of studies scoring above
and below predefined scores in two quality assessment scales were compared; (3) Primary
studies were consecutively entered into a cumulative meta-analysis according to the
summary scores derived from the quality assessment scales. All analyses were performed
using meta-regression methods. Studies that were explicitly randomized and were double-blind
as well as studies scoring above the cut-points yielded significantly less positive
results than studies not meeting the criteria. In the cumulative meta-analyses, there
was a trend for increasing effect sizes when more studies with lower-quality scores
were added. However, there was no linear relationship between quality scores and study
outcome. We conclude that in the study set investigated, there was clear evidence
that studies with better methodological quality tended to yield less positive results.
Because summarizing disparate study features into a single score is problematic, meta-regression
methods simultaneously investigating the influence of single study features seem the
best method for investigating the impact of study quality on outcome.
Keywords
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Article Info
Publication History
Accepted:
March 8,
1999
Identification
Copyright
© 1999 Elsevier Science Inc. Published by Elsevier Inc. All rights reserved.
