External quality assurance of molecular analysis of haemochromatosis gene mutations

The Royal College of Pathologists of Australasia Quality Assurance Programs has conducted an external quality assurance programme for the testing of the haemochromatosis gene (HFE) mutations C282Y and H63D.

A total of 10 surveys have been undertaken over a period of 6 years from 2000 to 2005.

Of the 3016 responses received, the overall success rate was found to be 99.47% (3000/3016). A total of 16 errors were found, 6 for C282Y and 10 for H63D. Only one sample was associated with more than one error, in which 2 of 23 respondents classified a normal sample as heterozygotic for H63D. Overall performance was observed to vary minimally between surveys, from a low of 91.3% correct (21/23 responses) for a normal sample to 100% correct in most (85/100) samples. Of the 10 complete surveys, four returned a 0% error rate. In one survey in 2004, seven incorrect responses were returned by one laboratory, all of which were secondary to transcriptional errors. Overall success rates per assay were 99.61% (1532/1538) for C282Y and 99.32% (1468/1478) for H63D. Over a period of 6 years from 2000 to 2005, the proportion of respondents using polymerase chain reaction (PCR) and restriction enzyme analysis fell from 85% to around 30%, whereas the proportion of laboratories using real-time PCR rose from 5% to around 55%, as indicated by the questionnaire surveys of methods used by participants.

Encouraging levels of testing proficiency for two common genetic mutations are indicated by these data, but they also confirm the need for participation of molecular diagnostic laboratories in external quality assurance programmes to ensure the ongoing provision of high-quality genetic testing services.