Classification of Axial Spondyloarthritis Inception Cohort (CLASSIC) study

Primary Objective

To validate the performance of the current ASAS classification criteria in a prospective combined cohort of patients presenting to a rheumatologist in North America and outside North America with undiagnosed current back pain of ≥3 months duration with onset ≤45years of age.

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The ASAS group has developed classification criteria for axial spondyloarthritis (axSpA) that allow the inclusion of patients with an early form of disease that is not yet clearly visible on plain radiography. These criteria include both an "imaging arm," that incorporates either radiographic sacroiliitis or magnetic resonance imaging (MRI) features of inflammation in the sacroiliac joints (SIJ) plus one clinical feature of spondyloarthritis (SpA), and a "clinical arm" that requires presence of the HLA B27 protein plus 2 clinical features of SpA.




Back pain greater than or equal to 3 months in duration, with onset less than or equal to 45 years of age.

Inclusion Criteria: Consecutive patients referred to rheumatologists with current undiagnosed back and/or buttock pain with onset <= 3 months will be screened for study eligibility verbally or by using a simple paper form provided by the medical secretary or a research coordinator at the first patient encounter. Patients will be asked to complete the following questions: 1. Do/did you have any back, buttock, or hip discomfort in the last week? (yes or no) If no, cannot consider current and therefore patient is not eligible 2. Have you had discomfort in your back, buttocks, or hips that has lasted at least three months? (yes or no) 3. If yes, did your first symptoms of pain begin when you were less than or equal to 45 years of age? (yes or no) If patient answers yes to questions 1, 2, and 3, the patient will be deemed potentially eligible. If the answer to these questions is no, patient will be deemed ineligible for the study and no patient data will be retained. Patients with a prior rheumatologist confirmed diagnosis of SpA at the time of referral to the study-affiliated investigation will not be considered eligible. Many patients in North America consider the sacroiliac region as "the hip". Consequently, study coordinators will be trained to recognize what constitutes appropriate pain localization for the purposes of study eligibility. Pain localized to the lateral aspect of the hip or groin will exclude study participation. If the patient is deemed eligible on the basis of the 3 questions this information will be entered in to the eCRF by the coordinator. Inclusion criteria will also include the ability and desire of the patient to complete the consent for data collection. This screening assessment will also allow the coordinator to blind the rheumatologist to the results of any CRP, HLA-B27, or imaging data that may have been ordered by the referring health care professional. the coordinator will inform the rheumatologist whether the patient is study eligible (only relevant to North America; blinding of the rheumatologist will not be done in participating ASAS centers outside North America).

Type of Study



Barbara Davis Center
Rocky Mountain Regional VA Medical Center
University of Colorado Hospital

Principal Investigator
Photograph of Liron Caplan,  MD, PhD

Liron Caplan, MD, PhD

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