Polymerase chain reaction based human leucocyte antigen genotyping for theinvestigation of suspected gastrointestinal biopsy contamination

Background-Mislabelling or contamination of surgical specimens may lead to diagnostic inaccuracy, particularly within gastrointestinal pathology when multiple small mucosal biopsy specimens are commonly taken, and where a tin y fragment of foreign tissue may be indistinguishable from true biopsy mate rial using histological assessment alone. Aims-To assess the utility of polymerase chain reaction (PCR) based human l eucocyte antigen (HLA) genotyping techniques for the investigation of poten tially mislabelled or contaminated gastrointestinal biopsy specimens. Patients-Ten cases (28 samples) in which mislabelling or contamination was suspected, comprising four upper gastrointestinal tract biopsies and six co lonoscopic biopsy series. Methods-Direct and nested PCR-sequence specific primer (SSP) based HLA clas s II genotyping was performed on DNA extracted from formalin fixed and para ffin wax embedded tissue (23 samples) or peripheral blood leucocytes (five samples). Results-A full HLA-DRB1 genotype was determined in all 28 samples. In seven cases the HLA-DRB1 genotype of the putative contaminant was different to t hat of the corresponding reference tissue, confirming different individual origins for the contaminant and reference material. In one case the contami nant tissue was shown to possess the same HLA-DRB1 alleles as a second pati ent (probable source). In the remaining three cases the same HLA-DRB1 allel es were detected within the potential contaminant and reference tissues. Conclusions-PCR based HLA class II genotyping is a valuable tool for invest igating potential contamination or mislabelling within gastrointestinal bio psy specimens and this report has confirmed contamination in seven of ten c ases studied.