Accurate Liability Estimation Improves Power in Ascertained Case Control   Studies
  Linear mixed models (LMMs) have emerged as the method of choice for confounded genome-wide association studies. However, the performance of LMMs in non-randomly ascertained case-control studies deteriorates with increasing sample size. We propose a framework called LEAP (Liability Estimator As a Phenotype, https://github.com/omerwe/LEAP) that tests for association with estimated latent values corresponding to severity of phenotype, and demonstrate that this can lead to a substantial power increase. 
Omer Weissbrod, Christoph Lippert, Dan Geiger, and David Heckerman
q-bio.GN stat.AP