HNF4A and diabetes mellitus: This substantial impact of ascertainment bias was seen at the individual variant level, consistent with other similar observations of LDL cholesterol levels in LDLR and APOB carriers in a different study population35,46 and HNF4A p.Arg114Trp in diabetes risk13 (HNF4A p.Arg114Trp was present in the present datasets, but filtered out due to its designation as a variant of uncertain significant (VUS), reflecting its known low penetrance).