Detection of Human Leukocyte Antigen B27 by Flowcytometry in Patients With Suspected Ankylosing Spondylitis in a Tertiary Care Centre.

Introduction Human leukocyte antigen B27 (HLA-B27) is strongly implicated in the pathogenesis of ankylosing spondylitis (AS). Hence, HLA-B27 testing is routinely used in the diagnosis of AS. Objectives We aimed to establish the frequency of HLA-B27 in AS patients by flow cytometry and relate the differences between B27+ and B27- cases to the serum concentrations of rheumatoid arthritis factor (RA), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). Methods  The study population included a total of 210 patients who visited the tertiary health care center. The peripheral blood samples obtained from AS patients were subjected to a qualitative two-color direct immunofluorescence method using the HLA-B27/CD3 antibody for the rapid detection of HLA-B27 antigen expression in erythrocyte-lysed whole blood in FACSCalibur flow cytometer (Becton Dickinson, USA). Results Out of 210 AS patients, the distribution of HLA-B27 positivity was observed only in 46 (22%) patients. The remaining 164 patients (78.1%) were negative for HLA-B27. Of the 46 HLA positive patients, 39 (25.34%) were males and only seven (12.5%) were females. In both sexes, HLA-B27 frequency was significantly higher in the age group 21-30 years, followed by 41-50 years. The current study also revealed a significant association between sex and age of onset of HLA‑B27 detection in patients with suspected AS. Disease activity was not significantly correlated with RA, ESR, and CRP. Conclusions The detection of HLA-B27 by flow cytometry proved to be a reliable test in the screening of AS in the Indian population.