Background/Purpose: HLA B27 prevalence in Latin America are heterogeneous and timeless, we propose to estimate the prevalence of HLA B27 in an Argentinian cohort of axial spondyloarthritis (SpA) and to evaluate the differences between positive and negative patients and to analyze its performance as a diagnostic biomarker.

Methods: An observational study included patients older than 18, with axial SpA diagnosis performed in a fast track evaluation program (Reuma-check SpA) between 2017-19. In this circuit, all patients underwent: blood tests, HLA B27, sacroiliac Rx, sacroiliac MRI and enthesitis ultrasound. Sociodemographic data and education level were also collected. SpA symptoms: Age of onset and characteristic of low back pain, SpA features, NSAIDs use and response, VAS: pain and night pain, time of morning stiffness. BASDAI, BASFI, MASES, HAQ was consigned. The clinical assessor was blinded to the complementary studies. For the sensitivity and specificity analysis, a group of patients with chronic low back pain who performed the same circuit in the same period of time were used as a control, paired 1:1 (gender and age).

Statistical analysis: descriptive statistics, Chi2 test or Fisher’s exact and Student or Mann Whitney test were performed. Binomial logistic regression was performed, and sensitivity, specificity, PPV, NPV and LR were calculated.

Results: 150 patients were included, 75 with axial SpA and 75 controls, the characteristics are showed in Table 1. The prevalence of HLA B27 in SpA patients was 43% (CI95: 30-53). The differences between positive and negative patients are shown in table 2. In the logistic regression analysis, BASFI values and the SpA features showed independent differences. When this prevalence was compared with those of the control group the difference was 43% vs 9% OR: 7.7 (IC95: 2.8-24), HLA B27 had a sensitivity: 43%, specificity: 91 %, PPV: 85%, NPV: 58% and LR: 4.9 (IC95: 3-8).

Conclusion: The prevalence of HLA B27 in axial SpA was 43%, positive patients had an earlier age of onset (36 years) and negative BASFI higher and more SpA features. For the diagnosis of SpA, HLA B27 had a good specificity but low sensitivity (91% vs 43).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-role-of-hla-b27-in-axial-spondyloarthritis-prevalence-and-performance-as-a-marker-in-an-argentinian-cohort/