title: A method for combining matched and unmatched binary data. Application to randomized, controlled trials of photocoagulation in the treatment of diabetic retinopathy.
abstract: A method for combining matched and unmatched data is described and was applied to the results of randomized, controlled trials of photocoagulation in the treatment of diabetic retinopathy. A pooled estimate from the matched and unmatched studies was obtained by adaptation of the Mantel-Haenszel method, where the strata were unmatched studies and matched pairs within studies. A test of significance was based on the Mantel-Haenszel chi-square statistic, the latter also being used to calculate test-based confidence intervals. A test of homogeneity was performed by combining Mantel-Haenszel chi-square statistics from the matched and unmatched studies. By these methods, the combined estimate of the risk of deterioration of visual acuity for those receiving photocoagulation (relative to a risk of unity for those not receiving photocoagulation) was 0.37 (95 per cent confidence interval 0.29-0.46). The chi-square statistic (1 df) for an effect of treatment was 87.75 (p less than 0.0001). The chi-square statistic for homogeneity of relative risk among studies was 11.20 (4 df, p less than 0.05). However, this result was influenced disproportionately by one small matched study.
authors.affiliation: MRC Biostatistics Unit, Cambridge, England.
authors.forename: S W
authors.initials: SW
authors.lastname: Duffy
authors.forename: T E
authors.initials: TE
authors.lastname: Rohan
authors.forename: D G
authors.initials: DG
authors.lastname: Altman
mesh_terms: D003930:Diabetic Retinopathy / Q000628:therapy*; D004812:Epidemiologic Methods; D006801:Humans; D008028:Light Coagulation; D011897:Random Allocation; D012107:Research Design; D013223:Statistics as Topic / Q000379:methods*