ASAS modification of the Berlin algorithm for diagnosing axial spondyloarthritis: results from the SPondyloArthritis Caught Early (SPACE)-cohort and from the Assessment of SpondyloArthritis international Society (ASAS)-cohort

• Published in: Annals of the rheumatic diseases Vol. 72; no. 10; p. 1646
• Main Authors: van den Berg, Rosaline, de Hooge, Manouk, Rudwaleit, Martin, Sieper, Joachim, van Gaalen, Floris, Reijnierse, Monique, Landewé, Robert, Huizinga, Tom, van der Heijde, Désirée
• Format: Journal Article
• Language: English
• Published: England 01-10-2013
• Subjects: Adult; Algorithms; Back Pain - etiology; Chronic Pain - etiology; Cohort Studies; Decision Support Techniques; Decision Trees; Diagnostic Errors; Female; HLA-B27 Antigen - blood; Humans; Male; Middle Aged; Sensitivity and Specificity; Spondylarthritis - complications; Spondylarthritis - diagnosis; Young Adult; Ankylosing Spondylitis; Magnetic Resonance Imaging; Spondyloarthritis
• ISSN: 1468-2060
• DOI: 10.1136/annrheumdis-2012-201884

To compare the original Berlin algorithm for diagnosing axial Spondyloarthritis (axSpA) with two modifications in the SPondyloArthritis Caught Early (SPACE)-cohort and the Assessment of SpondyloArthritis international Society (ASAS) axSpA criteria validation (ASAS)-cohort.
Patients in the SPACE-cohort (back pain ≥3 months, ≤2 years, onset <45 years) and the ASAS-cohort (undiagnosed chronic back pain) were diagnosed according to three algorithms: original (inflammatory back pain (IBP) mandatory), modification 1 (IBP defined by ≥3/5 IBP-features instead of ≥4/5) and modification 2 (IBP deleted as obligatory entry criterion, added as SpA-feature). Diagnosis by rheumatologist, ASAS axSpA criteria and likelihood ratio product were used as external standards to test the performance of the algorithms.
SPACE-cohort: Compared to the diagnosis by rheumatologist (either axSpA or no-axSpA), the original algorithm agreed in 120 patients (76.4%). Agreement decreased using modification 1 (119 patients; 75.8%), increased using modification 2 (125 patients; 79.6%). Sensitivity increased from 66.2% (original) to 72.3% (modification 1) and 78.5% (modification 2). Specificity decreased more using modification 1 (83.7% to 78.3%) than when using modification 2 (83.7% to 79.6%). ASAS-cohort: Compared to the diagnosis by rheumatologist (either axSpA or no-axSpA), the original algorithm agreed in 484 patients (70.7%). Agreement increased using modification 1 (520 patients; 75.9%) and modification 2 (548 patients; 80.0%). Sensitivity increased from 65.3% (original) to 77.9% (modification 1) and 79.6% (modification 2). Specificity decreased more using modification 1 (79.2% to 72.2%) than when using modification 2 (79.2% to 75.6%).
ASAS accepted a modified algorithm for diagnosing axSpA in which IBP is excluded as obligatory entry criterion and added as SpA-feature.