Background: Although MRI of the sacroiliac joints (SIJ) is the most sensitive imaging modality for early diagnosis of axial spondyloarthritis (axSpA) it is costly and not readily available. Therefore, clinicians still rely primarily on radiography. The relative degree to which radiography and MRI changes diagnostic ascertainment of axSpA in patients presenting with undiagnosed back pain has not been formally studied.
Objectives: We aimed to assess the relative impact of radiography and MRI evaluation on diagnostic ascertainment of axial SpA in patients presenting with undiagnosed back pain to rheumatologists, and the impact of central evaluation.
Methods: The multicenter Screening for Axial Spondyloarthritis in Psoriasis, Iritis, and Colitis (SASPIC) Study is aimed at early detection of axial SpA. Consecutive patients ≤45 years of age with ≥3 months undiagnosed back pain with any one of psoriasis, acute anterior uveitis (AAU), or colitis undergo routine clinical evaluation by a rheumatologist for axial SpA and MRI evaluation is ordered per rheumatologist decision. The rheumatologist determines the presence or absence of axial SpA at 3 consecutive stages: 1. After the clinical evaluation; 2. After the results of labs (B27, CRP) and radiography; 3. After the results of MRI evaluation. The eCRF, radiographs, and MRI scans were also assessed centrally.
Results: The SASPIC cohort comprises 246 patients (52.4% male, mean age 34.5 years, mean symptom duration 7.3 years, mean back pain duration 7.1 years, B27+ 36.2%) referred with AAU (29.7%), psoriasis (18.7%), Crohn’s colitis (31.3%), ulcerative colitis (20.3%). MRI was conducted in 149 patients. The number of patients diagnosed with axSpA by the local rheumatologist decreased after radiography and then decreased further after MRI while confidence in the diagnosis progressively increased (Table 1). After central evaluation of all patient data, the number of patients diagnosed with axSpA decreased substantially compared to assessment by local readers (Table 2).
Conclusion: In a setting of undiagnosed back pain and higher risk for axial SpA, imaging is primarily helpful in ruling out SpA and reducing false positives. Despite this, central evaluation raises concerns regarding ascertainment of false positive SpA in routine practice.
Disclosure of Interests: Walter P Maksymowych Grant/research support from: AbbVie, Pfizer, Janssen, Novartis, Consultant for: AbbVie, Eli Lilly, Boehringer, Galapagos, Janssen, Novartis, Pfizer and UCB Pharma; Chief Medical Officer for Canadian Research and Education Arthritis, Raj Carmona Grant/research support from: Amgen, Abbvie, Jannsen, Consultant for: Amgen, Abbvie, BMS, Eli Lilly, Merck, Novartis, Jannsen, Takeda, UCB, James Yeung: None declared, Jon Chan Grant/research support from: Janssen, UCB, Novartis, Pfizer, Celgene, Consultant for: Amgen, Celgene, Eli Lilly, Janssen, Amgen, Abbvie, Novartis, Pfizer, UCB, Sandoz, Merck, Liam Martin: None declared, Sibel Aydin Consultant for: Abbvie, Celgene, UCB, Novartis, Jannsen, Sanofi, Dianne Mosher: None declared, Ariel Masetto Grant/research support from: Amgen, Sanofi, Consultant for: Sanofi, Pfizer, Bristol-Myers Squibb, Novartis, Boehringer Ingelheim, Speakers bureau: Novartis, Stephanie Keeling Consultant for: AbbVie. Pfizer, Eli Lily, Janssen, Amgen, Astrzeeneca, UCB., Olga Ziouzina: None declared, Sherry Rohekar Consultant for: Abbvie, Amgen, BMS, Celgene, Eli-Lilly, Janssen, Merck, Novartis, Pfizer, Roche, Sanofi, UCB, Joel Paschke: None declared, Amanda Carapellucci: None declared, Robert G Lambert Consultant for: Bioclinica, Parexel, Abbvie
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