The New ASAS Classification Criteria For Axial And Peripheral Spondylarthritis: Valid In The Latin American Patients, But

Abstract

Background: Different Spondylarthritis (SpA) presentation pattern have been described in Latin American countries. The Undiferentiated Spondylarthritis (uSpA) and Reactive Arthritis (ReA) forms are frequent (about 75%), whereas Ankylosing Spondylitis (AS) is near to 25%. Mixtures of axial and peripheral manifestations are common at onset and during evolution of the disease. We assess the new ASAS classification criteria for axial and peripheral SpA in a cohort of Colombian patients with established diagnostic of the disease. Methods: Two hundred and eighty-one consecutive patients were evaluated in the last 10 years following the ASAS recommendations. Seventy four, with established diagnostic (by experts) were selected. All of them had complete clinical and laboratory information (including HLA-B27 screening), X-ray and magnetic resonance imaging of sacroiliac joints and were under 45 years old at the beginning of the disease. We also collected a control group: patients referred to our clinic in the same period of time with chronic back pain in which the diagnostic of SpA was ruled out, after following the same protocol. Summary of the Results: A total of 74 patients (58 males, 16 females) with definite SpA (15 AS, 39 uSpA and 20 ReA), and 48 controls (34 males, 14 females) were analyzed. Mean disease duration in SpA patients was 1,4_1,1 vs. 4,5_4,3 years; mean age at disease onset was: 25,2_7,3 vs. 30,5_7,6 years. The key clinical findings were: arthritis and enthesitis in 75,7% (vs. 4,2% in controls), and inflammatory back pain (IBP) in 56,8% of the patients (vs. 4,2%). The other differences between the groups were: twenty-seven (36,5%) HLA-B27 positive patients (vs. 4,2%); buttock pain present in 32,4% of the patients and only 8,3% of the controls. Dactylitis was present in 24,7% of the patients vs. 0% in the controls. Uveitis was documented in 10,8% of the patients but not in controls. The family history of SpA was present in 4,2% of the patients (0% in the controls). The new Axial SpA classification criteria had a sensitivity and specificity of 66,2 and 91,7%; and the peripheral SpA classification criteria had a sensitivity and specificity of 90,5 and 87,5% respectively. When we decided to test them combined, we obtained a sensitivity of 93,2% and specificity of 87,5%. The European Spondylarthritis Study Group (ESSG) criteria had a sensitivity and specificity of 91,9 and 100%. Conclusions: Although, the new ASAS classification criteria for axial and peripheral SpA show a good performance in our cohort, the predominant mixed form of the disease in the Latin American patients and low prevalence of HLA-B27 positivity should make us keep in mind the ESSG criteria. These results should be validated in a large group of patients.