HLA-B27 Testing in Clinical Practice: A Retrospective Analysis of Testing Indications and Rheumatology Referral Patterns.

Abstract

The HLA-B27 allele is strongly associated with spondyloarthritis (SpA). HLA-B27 is included in SpA classification criteria and referral strategies for axial SpA. Investigations of HLA-B27 testing in usual clinical practice are limited. We identified all adult patients tested for HLA-B27 from January 1, 2022, to December 31, 2022, in the Mass General Brigham healthcare system. We examined patient demographics; ordering provider specialty; testing indication; concurrent testing with antinuclear antibodies (ANA), rheumatoid factor, and/or anticyclic citrullinated peptide autoantibodies; and rheumatology referral. We compared the rate of rheumatology referral between HLA-B27-positive and HLA-B27-negative patients. HLA-B27 tests were ordered for 1960 patients (62.4% female; average age: 47.4 yrs). The most common specialties testing HLA-B27 were rheumatology (39.7%) and ophthalmology (21.4%). The most common indications for HLA-B27 testing were peripheral arthritis (33%), uveitis (22%), and back pain (16.7%). The majority of HLA-B27 tests (69.3%) were ordered concurrently with other autoantibody tests. A total of 11% of tested patients were HLA-B27 positive. Ophthalmology had the highest positive rate (15.4%), whereas reactive arthritis was the indication with the highest positive test rate (50%). A greater proportion of HLA-B27-positive patients were referred to rheumatology (53% vs 32%; <i>P</i> = 0.002). HLA-B27 testing was frequently performed by rheumatologists and nonrheumatologists for a broad spectrum of indications. Cotesting HLA-B27 with ANA and rheumatoid arthritis autoantibodies was common. Nearly half of HLA-B27-positive patients were not referred to rheumatology. Further efforts are needed to promote judicious use of HLA-B27 testing and optimize referral pathways to rheumatology.