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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References
- Empirical evidence of bias.JAMA. 1995; 273: 408-412
- The importance of quality of primary studies in producing unbiased systematic reviews.Arch Intern Med. 1996; 156: 661-666
- Does quality of reports of randomised trials affect estimates of intervention efficacy reported in meta-analyses?.Lancet. 1998; 352: 609-613
- Assessing the quality of randomized controlled trials.Control Clin Trials. 1995; 16: 62-73
- Quality scores are useless and potentially misleading.Am J Epidemiol. 1994; 140: 300-301
- Invited commentary.Am J Epidemiol. 1994; 140: 297-299
- Are the clinical effects of homoeopathy placebo effects? A meta-analysis of placebo-controlled trials.Lancet. 1997; 350: 834-843
- Assessing the quality of reports of randomized clinical trials.Control Clin Trials. 1996; 17: 1-12
- Randomized clinical trials of acupuncture for asthma—a systematic review.Fortschr Komplementärmed. 1996; 3: 148-155
- St John’s wort for depression—an overview and meta-analysis of randomised clinical trials.BMJ. 1996; 313: 253-258
- Meta-analysis in clinical trials.Control Clin Trials. 1986; 7: 177-188
- A random-effects regression model for meta-analysis.Stat Med. 1995; 14: 395-411
- Random-effects models of longitudinal data.Biometrics. 1982; 38: 963-974
- Classical homeopathic treatment of chronic headache.Cephalalgia. 1997; 17: 119-126
- Double-blind randomized placebo-controlled study of homoeopathic prophylaxis of migraine.Cephalalgia. 1997; 17: 600-604
- Randomized controlled trials of individualized homeopathy—a state-of-the-art review.J Alt Complement Med. 1998; 4: 371-388
- A method for assessing the quality of a randomized control trial.Control Clin Trials. 1981; 2: 31-39
- An empirical study of the possible relation of treatment differences to quality scores in controlled randomized clinical trials.Control Clin Trials. 1990; 11: 339-352
- Meta-analysis.in: Rothman K. Greenland S. Modern Epidemiology. Lippincott Raven, Philadelphia, PA1998
- Assessing the quality of randomized controlled trials. Current issues and future directions.Int J Technol Assessment Health Care. 1996; 12: 195-208
- Low-molecular weight heparin versus standard heparin in general and orthopedic surgery.Lancet. 1992; 340: 152-156
- Improving the quality of reporting of randomized trials.JAMA. 1996; 276: 637-639
Article info
Publication history
Accepted:
March 8,
1999
Identification
Copyright
© 1999 Elsevier Science Inc. Published by Elsevier Inc. All rights reserved.
