Routine molecular genotyping of HLA-B27 in spondyloarthropathies overcomes the obstacles of serological typing and reveals an increased B*2702 frequency in ankylosing spondylitis

Objective. To evaluate the reproducibility and reliability of polymerase chain reaction (PCR) in HLA-B27 typing compared to the conventionally used microlymphocytotoxicity test (MLCT). To determine the HLA-B27 subtype frequencies (B*2701-B*2709) in patients with HLA-B27 associated disease and healthy persons using sequence specific oligonucleotides (SSO). Methods. 398 consecutive patients were HLA-B27 typed by MLCT and PCR. Subtyping by SSO was performed in 142 patients with HLA-B27 associated disease ankylosing spondylitis (AS) n = 38, reactive arthritis 44, undifferentiated spondyloarthropathy (uSpA) 45, psoriatic arthritis 15] and 125 healthy HLA-B27 controls. Results. MLCT identified 61 HLA-B27 positive patients (15.3%); PCR identified 7 positive patients (19.6%). MLCT gave false negative results for 8 patients (2.0%) and false positives for a further 7 (1.8%). Only subtypes B*2702 and B*2705 were present in patients and controls. Overall frequencies of B*2702 in patients and controls were 14.1 and 9.6%, respectively. The B*2702 frequency was significantly (p corn < 0.04) higher in AS (23.7%) and lower in uSpA (6.7%) patients. Conclusion. HLA-B27 typing by PCR is reliable and reproducible and therefore recommended for routine typing. It overcomes the obstacles of serological typing, i.e., equivocal results and cross-reactivity. In addition, subtype frequencies (B*2702 and B * 2705) are equally distributed among patients and controls, although subtype B*2702 seems to be more frequent in AS and less so in uSpA.