Identifying patients with axial spondyloarthritis in primary care: how useful are items indicative of inflammatory back pain?

Abstract

Background: The value of clinical items defining inflammatory back pain to identify patients with axial spondyloarthritis (SpA) in primary care is unclear.

Objective: To identify predictive clinical parameters for a diagnosis of axial SpA in patients with chronic back pain presenting in primary care.

Methods: Consecutive patients aged < 45 years (n=950) with back pain for > 2 months who presented to orthopaedic surgeons (n=143) were randomised based on four key questions for referral to rheumatologists (n=36) for diagnosis.

Results: The rheumatologists saw 322 representative patients (mean age 36 years, 50% female, median duration of back pain 30 months). 113 patients (35%) were diagnosed as axial SpA (62% HLA B27+), 47 (15%) as ankylosing spondylitis (AS) and 66 (21%) as axial non-radiographic SpA (nrSpA). Age at onset ≤ 35 years, improvement by exercise, improvement with non-steroidal anti-inflammatory drugs, waking up in the second half of the night and alternating buttock pain were identified as most relevant for diagnosing axial SpA by multiple regression analysis. Differences between AS and nrSpA were detected. No single item was predictive, but ≥ 3 items proved useful for good sensitivity and specificity by receiver operating characteristic modelling.

Conclusion: This study shows that a preselection in primary care of patients with back pain based on a combination of clinical items is useful to facilitate the diagnosis of axial SpA.

Figure 1

Criteria for the recognition of axial SpA. Age at onset ≤35 years; wakening up in the second half of the night; alternating buttock pain; improvement by NSAIDs within 48 h or no NSAID; improvement by movement, not rest. The sensitivities and specificities for ≥4 criteria were 47.8 and 86.1%, for ≥3 criteria 78.8 and 46.4%, and ≥2 criteria 96.5 and 17.0%, respectively.NSAID non-steroidal anti-inflammatory drug; SpA, axial spondyloarthritis.