Asymptotic distributions of polylocus test statistics

Polylocus linkage analysis methods are modified two-point analyses which aim to approach the information gain of multilocus analysis. Terwilliger and Ott [(1992) Am J Hum Genet 51:A202, (1993) Genet Epidemiol 10:477-482] put forth two such methods. This paper presents asymptotic approximations to the null distribution of the likelihood ratio statistics for these two methods, correcting earlier reports [Terwilliger and Ott (1993) Genet Epidemiol 10:477-482; Schaid and Elston (1994) Genet Epidemiol 11:1-17]. The performance of the approximations is then assessed for finite samples of fully informative meioses.