Article type
Year
Abstract
Background: Empirical evidence of an association between unclear/inadequate allocation concealment in reports of randomised controlled trials (RCTs) [1,2,3,4] and inflation of the effect of the experimental intervention suggests that less confidence should be held in the results of RCTs with unclear or inadequate allocation concealment.
Objectives: Primary: to estimate the percentage of positive conclusions that remain supported by the data if only data from randomised trials with adequate allocation concealment are considered. Secondary: to estimate the percentage of these conclusions that are still supported by the data if an attempt is made to account for the expected overestimation associated with unclear or inadequate allocation.
Methods: Selection of reviews: Pairs of authors independently categorized allocation concealment in the primary trial publications of the RCTs included in 70 meta-analyses. Half of these were identified via PubMed among the most recent reviews indexed as meta-analyses and published in 2002, and half were a random sample of Cochrane Reviews published in 2003 issue 2. Inclusion criteria were: Independent agreement upon which intervention was the experimental and a conclusion stating a preference for one of the interventions (treatment or prophylaxis) based on a statistically significant binary outcome. Meta-analyses that comprised more than 40 RCTs, reviews where the conclusions referred to an indirect comparisons or where the conclusion was partly based on non-randomised trials, were excluded.
Analysis: The primary outcome will be obtained by re-meta-analysis of the subgroup of trials with adequate allocation concealment. For operational purpose conclusions are defined as insufficiently supported by the data, if the estimates derived from the subgroup analyses fail to reach statistical significance. The direction, magnitude and uncertainty of the differences between the overall estimates from the subgroup analyses and the original meta-analyses will be reported. A model for exploratory analysis to obtain the secondary outcome (not required to be valid on the level of the individual meta-analyses) is under development.
Results: Pending. Will be ready for colloquium.
Conclusion: Pending. Will be ready for colloquium.
References: 1. Jüni P, Altman DG, Egger M. Systematic reviews in health care: Assessing the quality of controlled clinical trials. BMJ. 2001;323(7303):42-6. 2. Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA. 1995;273(5):408-12. 3. Moher D, Pham B, Jones A et al. Does quality of reports of randomised trials affect estimates of intervention efficacy reported in meta-analyses? Lancet. 1998;352(9128):609-13. 4. Kjaergard LL, Villumsen J, Gluud C. Reported methodologic quality and discrepancies between large and small randomized trials in meta-analyses. Ann Intern Med. 2001;135(11):982-989.
Objectives: Primary: to estimate the percentage of positive conclusions that remain supported by the data if only data from randomised trials with adequate allocation concealment are considered. Secondary: to estimate the percentage of these conclusions that are still supported by the data if an attempt is made to account for the expected overestimation associated with unclear or inadequate allocation.
Methods: Selection of reviews: Pairs of authors independently categorized allocation concealment in the primary trial publications of the RCTs included in 70 meta-analyses. Half of these were identified via PubMed among the most recent reviews indexed as meta-analyses and published in 2002, and half were a random sample of Cochrane Reviews published in 2003 issue 2. Inclusion criteria were: Independent agreement upon which intervention was the experimental and a conclusion stating a preference for one of the interventions (treatment or prophylaxis) based on a statistically significant binary outcome. Meta-analyses that comprised more than 40 RCTs, reviews where the conclusions referred to an indirect comparisons or where the conclusion was partly based on non-randomised trials, were excluded.
Analysis: The primary outcome will be obtained by re-meta-analysis of the subgroup of trials with adequate allocation concealment. For operational purpose conclusions are defined as insufficiently supported by the data, if the estimates derived from the subgroup analyses fail to reach statistical significance. The direction, magnitude and uncertainty of the differences between the overall estimates from the subgroup analyses and the original meta-analyses will be reported. A model for exploratory analysis to obtain the secondary outcome (not required to be valid on the level of the individual meta-analyses) is under development.
Results: Pending. Will be ready for colloquium.
Conclusion: Pending. Will be ready for colloquium.
References: 1. Jüni P, Altman DG, Egger M. Systematic reviews in health care: Assessing the quality of controlled clinical trials. BMJ. 2001;323(7303):42-6. 2. Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA. 1995;273(5):408-12. 3. Moher D, Pham B, Jones A et al. Does quality of reports of randomised trials affect estimates of intervention efficacy reported in meta-analyses? Lancet. 1998;352(9128):609-13. 4. Kjaergard LL, Villumsen J, Gluud C. Reported methodologic quality and discrepancies between large and small randomized trials in meta-analyses. Ann Intern Med. 2001;135(11):982-989.