Background: Axial spondyloarthritis (axSpA) is a common extraintestinal manifestation of inflammatory bowel diseases (IBD). It is recommended to be diagnosed in patients with IBD by association of clinical features, such as Inflammatory Back Pain (IBP), and imaging, such as MRI and X-ray. In axSpA patients without IBD, Ankylosing Spondylitis Assessment Society (ASAS) criteria are used for defining IBP. Their diagnostic performance in patients with association of axSpA and IBD is not clear. The goal of the study was to evaluate the prevalence of Inflammatory Back Pain (IBP) in patients with IBD, and to explore the prognostic value of ASAS criteria for IBP in patients with IBD compared with imaging (MRI, X-ray) and ECCO consensus requirements for axSpA diagnosis in patients with IBD.
Methods: The study included 70 patients with IBD (Ulcerative Colitis (UC) - 45 patients (64.3%), Crohn's disease (CD) - 25 (35.7%), mean age 44±1.34 years). IPB was defined by ASAS criteria (2009). Patients, who fulfilled the ASAS criteria, or had back pain duration over 3 months and fulfilled 2–3 out of 5 ASAS criteria, imaging of lumbar spine and sacroiliac joints was performed (X-ray - 44 patients, including 21 with IBP; MRI (T1, STIR) - 25 patients, including 19 with IBP). Imaging was considered positive, if patients had at least unilateral sacroiliitis stage 2 or higher according to accepted grading system on X-Ray, or bone marrow oedema in sacroiliac joints on MRI.
Results: Low back pain was observed in 60 (85.7%) patients with IBD, 25 (35.7%) patients fulfilled the criteria ASAS for IBP. Radiographic changes were observed in 11 patients, 6 patients fulfilled the requirements of the modified New York classification criteria for ankylosing spondylitis. Osteitis on MRI was detected in 16 patients. Performance of the ASAS criteria was the following: sensitivity 76.2%, specificity 64.3%, PPV 61.5%, NPV 78.3%, LR+ 2.13, and LR- 0.37 (ECCO consensus definition used as the “gold standard”). Combination of ASAS criteria with MRI provided good discriminating power. X-ray didn't have any additional predictive value in patients with signs of IBP. In contrast, MRI doesn't have any additional predictive value in patients with no IBP.
Conclusions: IBP is a common finding in patients with IBD. The ASAS criteria for IBP were proved to be a valid instrument in patients with IBD. Performance parameters of the ASAS criteria in patients with IBD was comparable to the following in the general population of patients with axSpA.