Regional inference with averaged P values increases the power to detect linkage

Controversy exists with respect to the choice of an appropriate critical va lue when testing for linkage in a genomic screen. A number of critical valu es have been proposed for single-locus and multi-locus linkage analyses. In this study, criteria based on multiple single-locus analyses (i.e., region al test criteria) are evaluated using simulation methods for three differen t map densities. Tests based on single loci, multiple consecutive single lo ci, and moving averages of consecutive single loci are considered. Appropri ate critical values are determined based on results from simulations under the null hypothesis of no linkage. The power of each "regional test" was co mpared to the power of a single-locus test. Results suggest that the best p ower was found when averaging P values over an interval size of 9-15 cM, an d that testing the average of P values from two consecutive loci is superio r to testing each single locus separately. The increase in power ranged fro m 7-29% over the simulations considered. Genet. Epidemiol. 17:157-164, 1999 . (C) 1999 Wiley-Liss, Inc.