Meta-analysis combining parallel and cross-over clinical trials. II: Binary outcomes.
We examine different methods to pool binary outcomes used both in parallel and cross-over trials. Odds ratio (OR) estimators obtained from joint conditional probabilities in cross-over trials, such as the Mantel-Haenszel and Peto methods, are compared to an OR estimator using marginal results of cross-over trials. When there is correlation between the outcomes in the two cross-over periods, joint conditional ORs differ from marginal ORs and cannot be combined with OR estimates from parallel trials. The marginal OR estimate is independent of the between-period correlation and it includes a correction for cross-over correlation in the variance estimate. As its computation is similar in cross-over and parallel trials, it is the method of choice to pool results from parallel and cross-over trials in a combined design meta-analysis.
Curtin
François
F
Medical Statistics Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1 7HT, UK. francoiscurtin@compuserve.com
Elbourne
Diana
D
Altman
Douglas G
DG
D000419:Albuminuria; D002986:Clinical Trials as Topic / Q000379:methods*; D018592:Cross-Over Studies; D003928:Diabetic Nephropathies / Q000178:diet therapy; D003930:Diabetic Retinopathy / Q000628:therapy; D018753:Diet, Protein-Restricted; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D008028:Light Coagulation; D015201:Meta-Analysis as Topic; D016017:Odds Ratio; D013223:Statistics as Topic / Q000379:methods*