SAT0258 Identification of axial spondyloarthritis among patients with chronic back pain in primary care – does determination of HLA B27 improve the performance of clinical assessments of inflammatory back pain?

Abstract

Background The value of a combination of items defining inflammatory back pain (IBP) to screen for axial spondyloarthritis (SpA) in primary care has recently been studied. However, whether and how measurement of the HLA B27 status contributes to that is not clear. Objectives To study the additional value of HLA B27 determination as screening parameters for axial SpA in a cohort of patients with chronic back pain. Methods Consecutive patients <45 years (n=950) with back pain >2 months who presented to orthopedic surgeons (n=143) were randomized based on 4 primary key questions related to inflammatory back pain (IBP) for referral to rheumatologists (n=36) who made the diagnosis. HLA B27 was either assessed in primary or in secondary care. The primary outcome was the predictive value of a combination of items for a diagnosis of axial SpA. Logistic regression analyses and modeling techniques were used for the statistical analyses. Results Rheumatologists saw 322 randomly selected representative patients, mean age 36 years (y), 50% female, median duration of back pain 30 months: 113 patients were diagnosed as axial SpA (35%), 62% B27+, 47 as ankylosing spondylitis (AS, 15%), 66 as non-radiographic axial SpA (nr-axSpA, 21%). Major differences between AS and nr-axSpA have been described. Excluding HLA B27 from the analysis led to a list of criteria ≥4 of which had a sensitivity and specificity of 58.4 and 70.8%, respectively (area under ROC 69%). Adding HLA B27 to the analyses induced changes in the list of relevant items: past/present enthesitis came in, and the sensitivity (68.1%) but not the specificity (68.4%) of the criteria list improved (area under ROC 73.8%). Conclusions This study shows that patients with axial SpA can be identified by different methods in primary care. Combining HLA B27 and clinical items indicative of IBP increased the likelihood of having axial SpA in primary care. References Braun A, Saracbasi E, Grifka J, Schnitker J, Braun J. Identifying patients with axial spondyloarthritis in primary care: how useful are items indicative of inflammatory back pain? Ann Rheum Dis 2011;70:1782-7. Disclosure of Interest None Declared