Two tests of association for a susceptibility locus for families of variable size: An example using two sampling strategies

A two-stage approach was used to analyze Problem 2 simulated data from Gene tic Analysis Workshop 11. In the first stage, we tested for linkage with th e Haseman-Elston test in SIBPAL. Markers that were significant in the first stage were followed up with two types of association tests. These associat ion tests differ in the type of family information used: 1) parental transm issions to affected children or 2) differences in marker allele frequencies between affected and unaffected siblings. We also explored how the conclus ions changed when different sampling strategies were used. Of particular in terest was whether the entire data set should be used to test for both link age and association or whether the data set should be halved to allow for r eplication of the initial association results. (C) 1999 Wiley-Liss, Inc.