 Confirmation of ALD after positive plasma VLCFA determination usually involves molecular genetic analysis of "ABCD1".In females, where plasma VLCFA measurement is not always conclusive (some female carriers will have normal VLCFA in plasma), molecular analysis is preferred, particularly in cases where the mutation in the family is known.Although the clinical phenotype is highly variable among affected males, the elevations of VLCFA are present in all males with an "ABCD1" mutation.