The CASECONTROL Procedure

An individual’s genotype for a marker is considered missing if at least one of the alleles at the marker is missing. Any missing genotypes are excluded from all calculations. However, the individual’s nonmissing genotypes at other loci can be used as part of the calculations. If an individual has a missing trait value, then that individual is excluded from all calculations.

When the STRATA statement is used, missing stratum levels are handled in one of two ways: when the MISSING option is specified, missing values are treated as another stratum level; otherwise, individuals with a missing value for any of the STRATA variables are excluded from the analysis.