DIFFERENT STATISTICAL-MODELS USED IN THE CALCULATION OF THE PREVALENCE OF INSULIN-DEPENDENT DIABETES-MELLITUS ACCORDING TO THE POLYMORPHISMOF THE HLA-DQ REGION

The use of three statistical models yielded different estimates of the odds ratio relative to the association between the polymorphism in th e HLA-DQ region and insulin-dependent diabetes mellitus (IDDM). The mo dels used were: (1) the allele-dosage model which assumes that the num ber of susceptibility alleles has a linear effect on the logarithm of the odds; (2) the reference cell coding method used with alleles of su sceptibility as a risk factor; or (3) a model that uses a classificati on of alpha/beta heterodimers as a susceptibility factor. We suggest t hat models which imply a log-linear relationship between a susceptibil ity marker and disease such as the first model are not appropriate in the assessment of the HLA-IDDM association. In contrast, although both latter models are valid, the third model is more compatible with curr ent hypotheses of the pathological process of the disease. Once an est imation of the odds ratio is chosen, we use such an estimation to calc ulate an approximation of the prevalence of IDDM according to the poly morphism in HLA-DQ region using the iterative procedure of Newton-Raph son. These approaches are illustrated with data from a case-control st udy previously conducted in the city of Santiago, Chile.