The Experience of HLA-B27 Test Using Flowcytometry

Shin, Bo Moon

Abstract

BACKGROUND: HLA-B27 is associated with an increased incidence of specific spondyloarthropathies(SpA), most notably ankylosing spondylitis(AS). I evaluated the cases referred for HLA-B27 antigen using flowcytometry (FCM) to find the clinical characteristics of the patients and the diagnostic utilities of median fluorescence intensity (MFI) in HLA-B27 program.
METHODS
I evaluated 443 subjects of HLA-B27 cases using FACScan flowcytometry, consisted with software for automated calibration and analysis, calibration beads, and the anti-HLA- B27 fluorescein isothiocyanate (FITC)/anti-CD3 phycoerythrin (PE) monoclonal antibodies (all from Becton Dickinson, San Jose, CA).
RESULTS
Of the total 443 cases, the positive rate in male cases was 44% (132/300) and it was higher than that of female cases (22.4%, 32/143). The gating procedure was failed in one sample of 443 (0.23%). The positive rates in each diagnostic criteria were as follows; AS 61.6%, gout 20.0%, herniated intervertebral disc 20%, lower back pain 25.6%, polyarthritis 16.0%, psoriatic arthritis 20.0%, rheumatoid arthritis 28.3%, reactive arthritis 26.9%, SpA, undifferentiated 31.8% and uveitis/iritis 23.8%. In AS group, 89 cases (95.7%) showed MFI values higher than 150.
CONCLUSION
About 62% of AS group showed HLA-B27 positivity using FCM and the positive rates of other diseases group in SpA categories were around 20-30%. If we considered MFI value 150 as differential value, about 95% of HLA-B27 positive AS cases might not need further confirmatory study to differentiate HLA-B7.