DNA tests for HFE mutations associated with HH are available in some clinical laboratories and reference laboratories. Testing for the presence of the C282Y is essential, although most labs also test for H63D and S65C mutations.
Molecular testing involves the extraction of DNA from leukocytes in whole blood samples or from buccal cells. The DNA is then analyzed for specific HFE mutations using polymerase chain reaction (PCR) with melt curve analysis. Currently there are no FDA-cleared products for HFE testing, and testing laboratories are using laboratory-derived test reagents. This situation is expected to change as manufacturers submit products for FDA approval.
Molecular testing is considered most appropriate for confirmatory testing of symptomatic individuals with altered iron studies (increased TS and SF), in pre-symptomatic individuals (increased TS, normal SF and liver function tests), and in first degree family members of individuals diagnosed with HH.
The use of genetic tests alone for routine screening of asymptomatic persons is not recommended for several reasons.
- A positive test indicating the presence of HFE mutations does not guarantee that an individual will develop clinically significant iron overload or predict severity of symptoms.
- A negative result (no HFE mutations present) does not rule out a diagnosis of iron overload because of genetic heterogeneity.
- Compared to biochemical analyses for iron, molecular assays are expensive.
- Molecular testing may result in the diagnosis of a genetic disease, thus opening up the possibility for discrimination in health insurance coverage.