High rates of variation in HLA-DQ2/DQ8 testing for coeliac disease: results from an RCPAQAP pilot program

Abstract

AimCoeliac disease(CD) is a highly prevalent, gluten-dependent, autoimmune enteropathy. While the diagnosis is based on serological and histological criteria, genotyping of the human leucocyte antigens (HLA) DQ2 and DQ8 has been shown to have substantial clinical utility, especially in excluding the diagnosis in patients who do not carry either antigen. As a result, HLA genotyping is now being performed by more laboratories and has recently become one of the most frequently requested genetic tests in Australia. To date, there has been little scrutiny on the accuracy and reporting of results by laboratories new to HLA typing. In response to clinician feedback that identified potentially clinically significant discrepancies in HLA typing results, the Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP) undertook a pilot study to assess laboratory performance in the detection of HLA-DQ2/DQ8 and their associated HLA-DQA1 and HLA-DQB1 alleles.MethodsDNA was extracted from 5 patients and sent to 10 laboratories for external quality assurance (EQA) testing. Laboratories were assessed for reporting in genotyping, interpretation and methodology.ResultsOur findings showed that at least 80% of laboratories underperform with respect to recommended guidelines for HLA typing and reporting for CD, with 40% of laboratories failing to provide any clinical interpretation or full genotyping data. This suboptimal level of reporting may lead to ambiguities for downstream clinical interpretation that may compromise patient management.ConclusionsThese findings highlight the importance of adherence to standardised guidelines for optimal performance and reporting of HLA results and substantiate the need for EQA and proficiency testing for laboratories providing this service.