Citations

ObjectiveInflammatory back pain (IBP) is often an early manifestation of spondyloarthritis (SpA), but the prognosis of patients with incident IBP is unknown. This study was undertaken to investigate long‐term outcomes in patients with IBP, and predictors of progression to SpA, in a population‐based cohort.MethodsWe conducted a retrospective, longitudinal study using the Rochester Epidemiology Project, a longstanding population‐based cohort of residents of Olmsted County, MN. Patients ages 16–35 years with clinical visits for back pain from 1999 to 2003 were identified, and we screened these patients for the presence of new‐onset IBP and performed medical record reviews to collect data on clinical, laboratory, and imaging features of SpA. Outcomes in these patients were followed up until July 2016. We used survival analysis for competing risks to examine progression to either SpA, a non‐SpA diagnosis, or resolution of back pain. Recursive partitioning was used to identify predictors of progression to SpA.ResultsAmong 5,304 patients with back pain, we identified 124 patients with new‐onset IBP. After a median follow‐up of 13.2 years, IBP had progressed to SpA in 39 patients, 15 patients developed a non‐SpA diagnosis, and 58 patients had resolution of IBP. At 10 years, the probability of having SpA was 30%, while the probability of resolution of IBP was 43%. The most important predictors for progression to SpA were uveitis, male sex, and family history of SpA.ConclusionIn a minority of patients, new‐onset IBP progresses to SpA, while IBP resolves in many. That IBP often resolves may explain the difference between the prevalence of IBP (3–6%) and the prevalence of SpA (0.4–1.3%).

ObjectiveThe long‐term outcome of patients with nonradiographic axial spondyloarthritis (SpA) is unclear, particularly whether few or most progress to ankylosing spondylitis (AS). Our objective was to examine the progression to AS in a population‐based inception cohort of patients with nonradiographic axial SpA.MethodsThe Rochester Epidemiology Project (REP) is a longstanding population‐based study of health in the residents of Olmsted County, Minnesota. We searched the REP from 1985 to 2010 using diagnostic and procedural codes for back pain, HLA–B27, and magnetic resonance imaging of the pelvis, and we performed detailed chart reviews to identify subjects who fulfilled the Assessment of SpondyloArthritis international Society classification criteria for axial SpA but did not have AS. We followed these subjects from disease onset to March 15, 2015, and used survival analysis to measure the time to progression to AS.ResultsAfter screening 2,151 patients, we identified 83 subjects with new‐onset nonradiographic axial SpA. Over a mean follow‐up of 10.6 years, progression to AS occurred in 16 patients. The probability that the condition would remain as nonradiographic axial SpA at 5, 10, and 15 years was 93.6%, 82.7%, and 73.6%, respectively. There was more frequent and more rapid progression among subjects in the imaging arm (n = 18) than among those in the clinical arm (n = 65) (28% versus 17%; hazard ratio 3.50 [95% confidence interval 1.15–10.6], P = 0.02).ConclusionProgression to AS occurred in a minority (26%) of patients with nonradiographic axial SpA over as long as 15 years of follow‐up. This suggests that the classification criteria for nonradiographic axial SpA identifies many patients in whom the condition is unlikely to progress to AS or that nonradiographic axial SpA represents a prolonged prodromal state that takes longer to evolve to AS and thus requires longer follow‐up.