FALSE-NEGATIVE SEROLOGICAL HLA-B27 TYPING RESULTS MAY BE DUE TO ALTERED ANTIGENIC EPITOPES AND CAN BE DETECTED BY POLYMERASE CHAIN-REACTION

Serological typing with the microlymphocytotoxicity test (MLCT) and fl ow cytometry (FC) using HLA-B27 antisera is commonly used for the dete rmination of HLA-B27. However, in some patients tested more than once, negative results have turned out to be positive at following investig ations. We retested by polymerase chain reaction (PCR) samples from 20 randomly selected patients with reactive arthritis or Reiter's syndro me who had now been followed for 20 pr. Ten of the patients were origi nally tested to be HLA-B27 positive and 10 HLA-B27 negative by the MLC T. All 10 serologically HLA-B27 positive individuals were also positiv e in the PCR. However, 2/10 patients interpreted as being HLA-B27 nega tive were positive by PCR. At this time, the same two patients were al so positive in the routine MLCT and FC using four different monoclonal antibodies against HLA-B27. PCR is superior to serological techniques to determine HLA-B27 positivity unequivocally, since it is based on t he detection of HLA-B27 gene sequences.