USING RISK CALCULATION TO IMPLEMENT AN EXTENDED RELATIVE PAIR ANALYSIS

A new nonparametric method of linkage analysis is described based on i dentity by descent relationships between all pairs of affected relativ es within a pedigree. This approach is an extension of ESPA, which onl y uses information from pairs of affected siblings. The new method, ca lled ERPA, uses the risk calculation facilities of the LINKAGE program s to obtain the necessary information in a fashion which is simple to implement and which automatically generalizes to allow for marker loci which may be multiple, non-codominant and sex-linked. We have investi gated the relative performance of ERPA, ESPA and the lod score method on simulated data. ERPA appears to be more sensitive than ESPA for det ecting linkage in pedigrees with small sibships, though both nonparame tric methods are inferior to the lod score method when the true mode o f transmission can be specified.