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
- Rosaline van den Berg1,
- Manouk de Hooge1,
- Martin Rudwaleit2,
- Joachim Sieper3,
- Floris van Gaalen1,
- Monique Reijnierse4,
- Robert Landewé5,
- Tom Huizinga1,
- Désirée van der Heijde1
- 1Department of Rheumatology, Leiden University Medical Center, Leiden, the Netherlands
- 2Department of Medicine, Endokrinologikum Berlin, and Charité University Medicine, Berlin, Germany
- 3Rheumatology Unit, Charité Medical University, Germany
- 4Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
- 5Department of Medicine, Division of Rheumatology, Academic Medical Center, Amsterdam, The Netherlands
- Correspondence to Professor Désirée van der Heijde, Department of Rheumatology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands;
- Accepted 7 October 2012
- Published Online First 8 November 2012
Objective 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.
Methods 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.
Results 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%).
Conclusions ASAS accepted a modified algorithm for diagnosing axSpA in which IBP is excluded as obligatory entry criterion and added as SpA-feature.