Abstract
IntroductionChronic back pain (CBP) is frequently the presenting symptom in patients with suspected axial spondyloarthritis (axSpA). Presence of sacroiliitis on magnetic-resonance-imaging (MRI) or HLA-B27 adds to diagnostic certainty. However, these costly tests cannot be applied in all patients with CBP. This study aims to investigate which SpA features increase the likelihood of a positive HLA-B27 or positive MRI of the sacroiliac-joints (MRI-SI) in patients with suspected axSpA.MethodsData from 665 patients with CBP within the ESPeranza Programme were analysed. Diagnostic utility measures (LR+, LR−) for a positive MRI-SI or HLA-B27 were calculated for various definitions of inflammatory back pain (IBP), their separate items and for other SpA features.ResultsPretest probabilityies of a positive result was 41 % for MRI-SI and 40 % for HLA-B27. For a positive MRI-SI result the most useful IBP characteristic was alternating buttock pain (LR + =2.6). Among the IBP-criteria, fulfillment of the ‘ASAS criteria’ (LR + =2.1) was most contributory. Interestingly, the addition of alternating buttock pain to the Calin/ASAS-IBP criteria (LR + =6.0 and 5.5, respectively) or the addition of awakening at second half of night to the Calin-IBP criteria (LR + =5.5) increased the pre-test probability of MRI-sacroiliitis from 41 % to 79–80 %. Dactylitis (LR + =4.1) and inflammatory bowel disease (IBD) (LR + =6.4) increased this probability to 73 % and 81 %, respectively. To forecast HLA-B27 positivity, awakening at the second half of the night, fulfillment of the ASAS-IBP definition and uveitis were the most useful, but only marginally predictive (LR + = 1.3, 1,6 and 2.6, respectively).ConclusionsIf patients with suspected axial SpA have either 1) IBP according to Calin/ASAS definition plus alternating buttock pain, or 2) IBP according to Calin definition plus awakening at night, or 3) dactylitis or 4) IBD, the probability of finding a positive MRI-SI increases significantly.
Highlights
Chronic back pain (CBP) is frequently the presenting symptom in patients with suspected axial spondyloarthritis
If patients with suspected axial SpA have either 1) inflammatory back pain (IBP) according to Calin/Assessment of SpondyloArthritis International Society (ASAS) definition plus alternating buttock pain, or 2) IBP according to Calin definition plus awakening at night, or 3) dactylitis or 4) inflammatory bowel disease (IBD), the probability of finding a positive MRI of the sacroiliac-joints (MRI-SI) increases significantly
For most of them (n = 653; 98.2 %) data was available on HLAB27 testing, and these were included in the analysis to evaluate the association between IBP characteristics and the presence of human leucocyte antigen B27 (HLA-B27)
Summary
Chronic back pain (CBP) is frequently the presenting symptom in patients with suspected axial spondyloarthritis (axSpA). Presence of sacroiliitis on magnetic-resonance-imaging (MRI) or HLA-B27 adds to diagnostic certainty These costly tests cannot be applied in all patients with CBP. It would be very helpful for rheumatologists to identify which referred patients have the highest likelihood of being diagnosed as having axSpA Such features of SpA that can be obtained by taking history or by simple physical examination, could potentially contribute to an efficient test-sequence to be applied in patients presenting with CBP and to optimise the use of supplementary tests in these patients. This study aims to investigate which features of SpA may increase the pre-test probability of a positive test result of HLA-B27 or MRI-SI in patients with suspected axSpA, which is a step forward in making a diagnosis of axSpA
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