Objectives To determine the prevalence of increased C reactive protein (CRP) in patients with recent inflammatory back pain (IBP) suggestive of spondylarthritis (SpA) and to describe the overall features of these patients.

Methods The DESIR cohort is a prospective multicenter French cohort of 708 patients with early IBP suggestive of SpA. An abnormal acute phase reactants level was determined based on normal upper range of values determined by centralized assessment of CRP. Data on the baseline demographic characteristics, functional status and quality of life, imaging features and HLA B27 status were compared in patients with and without increased CRP. We studied the total population of 708 patients and the subgroup of patients fulfilling ASAS criteria at the inclusion. Significant parameters in univariate analysis were tested in multivariate models.

Results The prevalence of increased CRP (>5mg/L) at inclusion in the DESIR cohort was 233/684 (34.1%). The presence of increased CRP was significantly associated (univariate) with a younger age, previous history of arthritis, a history of dactylitis, clinical synovitis, BMD, radiographic sacroiliitis, a higher baseline modified Score of Ankylosing Spondylitis Spinal Score (mSASSS), MRI inflammatory lesions of spine and sacroiliac joints, scores of disease activity including Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity (ASDAS-CRP), physical function assessed by Bath Ankylosing Spondylitis Functional Index (BASFI), and health status indicators (Ankylosing Spondylitis Quality of Life, Health Assessment questionnaire for Ankylosing Spondylitis and the Physical Component Score from Short Form 36) in both populations. Increased CRP was associated with the absence of HLA-B27 only in the subgroup of patients fulfilling ASAS criteria.

Stepwise multivariate analysis found an association between increased CRP and male gender, younger age, history of arthritis, BMD >25kg.m², radiographic sacroiliitis, mSASSS, MRI inflammation on sacroiliac joints and ASDAS-CRP (p<0,05).

Conclusions In recent IBP suggestive of SpA, increased CRP is associated with younger age, presence of peripheral articular manifestations, radiologic abnormalities, and both with higher activity and functional disability. Patients with elevated acute phase reactants seem to have a more severe form of the disease.

Disclosure of Interest None declared