HLA B27 typing in 511 children with juvenile idiopathic arthritis from India
The enthesitis-related arthritis (ERA) category of juvenile idiopathic arthritis (JIA) is the most common category in India. HLA B27 has a high prevalence in ERA, and ILAR classification includes it in exclusion criteria for other categories, but due to its cost, it is not routinely done. We undertook this study to assess the prevalence of HLA B27 in ERA and other groups of juvenile arthritis in India. Consecutive patients of JIA ERA and select patients from other categories were recruited from a single tertiary care hospital over a span of 3 years. HLA B27 was tested using PCR. Five hundred and eleven children were studied: 312 had ERA, and 199 had other categories (29 oligoarthritis, 107 polyarthritis, 44 systemic onset JIA, 9 psoriatic arthritis and 10 undifferentiated). The prevalence of HLA B27 was highest in the ERA group (87 %) and correlated with the presence of sacroiliitis. Prevalence was 10.3 % in oligoarthritis, 16 % in polyarticular rheumatoid factor (RF)-positive arthritis, 26 % in RF-negative polyarticular arthritis, 66 % in psoriatic arthritis and 40 % in the unclassified and 0 % in systemic onset category. Twenty-seven children had a change in category of JIA as per ILAR owing to HLA B27 testing positive, most commonly in the RF-negative polyarthritis group. Only six of these had clinical features suggestive of Spondyloarthropathy. There is high prevalence of HLA B27 in ERA. Though HLA B27 testing helps in correct classification, a minority of these patients have features suggestive of spondyloarthropathy like back pain, enthesitis or sacroiliitis.