Objectives To identify clinical, laboratory, and radiological findings that may increase the probability of making a diagnosis of spondyloarthritis (SpA) by the treating rheumatologist. Additionally, the association of the same variables with the fulfillment of ASAS criteria was analysed.
Methods Cross-sectional study of all patients with new-onset SpA included in the participating units within the ESPERANZA program. Selection criteria for Esperanza were: Patients under 45 years of age with at least a two-year history of inflammatory back (IBP) pain; back or joint pain in the presence of psoriasis, anterior uveitis, radiographic sacroiliitis, family history of SpA or positive HLA-B27; or asymmetric arthritis. The dependent variable was the diagnosis by the treating rheumatologist from the SpA Unit and the fulfillment of the ASAS criteria for the second objective. The following were tested as predictive variables: sex, presence of IBP, talalgia, any enthesitis, arthritis, psoriasis, uveitis, inflammatory bowel disease (IBD), and good response to NSAIDs. As laboratory results, elevated CRP and HLA-B27, were also considered; for imaging, we also tested the presence of sacroiliitis on radiography (according to NY criteria) or on magnetic resonance imaging (MRI, according to ASAS definition). The association of these parameters to either a diagnosis of SpA or to the ASAS classification was analyzed by multivariate logistical regression analysis.
Results 1179 patients in the ESPERANZA program were eligible for this analysis, among whom lumbar pain was the primary reason for referral (73.3%). The mean age of the population was 33.2±7.1 years with 53.8% men. The mean time from the onset of symptoms was less than one year (11.5±6.5 months). A diagnosis was made by the treating physician in 815 patients, who were then included in the analysis. 74% (603) of these patients were diagnosed with a SpA; additionally 52.6% met the ASAS criteria, peripheral ASAS in 31.3% and full ASAS in 69.7%. All parameters analyzed showed a statistically significant association with a diagnosis of SpA except for the presence of uveitis, IBD, and elevated C-RP levels. The parameters associated with higher odds were radiological sacroiliitis (OR 32.4), IBP (OR 28.9) and the presence of bone edema on MRI (OR 6.6). Similarly, in the classification by ASAS criteria, all parameters were statistically significantly associated except for the presence of IBD and increased acute-phase reactants; the parameters with the largest influence were sacroiliitis on radiograph (OR 60.5) and on MRI (OR 51.7), as well as positive HLA-B27 (OR 12.6).
Conclusions The presence of sacroiliitis on image studies is the parameter that most significantly influences both the diagnosis and the classification of patients; this study demonstrates that sacroileitis on MRI plays a very important role in this sense. The presence of IBP is the clinical parameter that most influences the diagnosis of SpA and it has become apparent that HLA-B27 plays a very important role in the classification by ASAS criteria.
Disclosure of Interest E. Tomero Grant/Research support from: ESPERANZA PROGRAM has been supported by an unrestricted grant from Pfizer, L. Carmona: None Declared, J. Mulero: None Declared, E. de Miguel: None Declared, M. Gobbo: None Declared, C. Martínez: None Declared