To describe how patients presenting with inflammatory back pain (IBP) of short duration can be classified by different sets of classification criteria for spondyloarthritis (SpA) and ankylosing spondylitis, and which clinical and imaging features are of discernible importance.
68 patients with IBP of a maximum of 2 years' duration were included in the early spondyloarthritis cohort. Detailed history, clinical examination and imaging of sacroiliac joints by plain radiography and magnetic resonance imaging (MRI) were obtained. The Berlin criteria set for SpA that has a prominent place for MRI and human leucocyte antigen B27 was used to quantify the relative contribution of MRI in classifying SpA.
14 of the 68 patients had ankylosing spondylitis according to the modified New York criteria, 57 patients fulfilled the European Spondylarthropathy Study Group (ESSG) criteria for SpA, 48 patients fulfilled the Amor criteria for SpA (43 patients fulfilled both criteria sets) and 44 patients fulfilled the Berlin criteria for SpA. Only four patients did not fulfil any criteria set; 36 patients fulfilled ESSG, Amor and Berlin criteria. The 14 patients with ankylosing spondylitis fulfilled all three SpA criteria sets.
Among our selected cohort of patients with early IBP, the prevalence of SpA according to three different criteria sets is high. The ESSG criteria were the most sensitive, followed by the Amor criteria and the Berlin criteria. The modified New York criteria for ankylosing spondylitis appeared to be the most specific. In this cohort, the contribution of MRI and human leucocyte antigen B27 to purely clinical criteria in making a diagnosis of axial SpA was limited.