Heteroduplex analysis for the three common HFE variants: methodology, reliablity and analysis of over 5000 requests for testing

Abstract

Objective: To describe the analysis of over 5300 patient samples for the HFE genotype. Methods: Blood samples received from hospitals in England, Wales and Ireland were analysed with a single, multiplex PCR using heteroduplex generators for the C282Y, H63D and S65C variants of the HFE gene. PCR products labelled with fluorescent dyes were analysed by capillary electrophoresis. Genotype frequencies were analysed according to the reasons given for testing. Results: Analysis of 400 samples sent in duplicate revealed one error that was associated with reporting rather than the methodology. Of 5327 samples received, 1122 were for family testing, 2470 for diagnostic testing and in 1735 cases no reason was given. Overall, homozygosity for C282Y was found in 14% of samples received for family testing and in 16% of the remaining samples. Clinical indications such as ''liver disease'' were of little predictive value for homozygosity for C282Y, but this increased if a raised serum ferritin concentration or transferrin saturation was indicated. When the diagnosis was iron overload, 39% of subjects tested were homozygous for C282Y. Compound heterozygosity (C282Y/H63D) was more frequent than in the general population but the frequency was not further increased in subjects for whom there was a diagnosis of iron overload. The frequencies of heterozygosity for H63D or S65C and homozygosity for H63D were not significantly increased in any group compared with the general population frequency.Conclusion: These results demonstrate the reliability of the methodology and confirm the difficulty of identifying genetic haemochromatosis purely on the basis of clinical suspicion that haemochromatosis may be responsible for liver disease, diabetes or arthritis. 2 Once diagnosed, HH is readily treatable by the means of venesection and, provided complications have not arisen, life expectancy is not reduced.3-5 The allele frequency of HFE C282Y in people of northern European origin in the UK is about 8% with about one in seven people being heterozygous, and one in 150 being homozygous for the C282Y allele. 6 The frequency, availability of a genetic test and an effective treatment have led to pressure to implement population screening 7 although there were always concerns about the clinical penetrance of HFE mutations. 8 These concerns were justified as it is now clear that although most men, and about 50% of women, who are homozygous for C282Y will show evidence of iron accumulation (a raised transferrin saturation) the clinical penetrance of homozygosity for C282Y is low.9-11