The risk, predictors and outcomes of amyloidosis in ankylosing spondylitis: a longitudinal population-based cohort study

Objectives: The risk of amyloidosis during the course of AS is yet to be firmly established. We aimed to evaluate the risks, predictors and prognostic outcomes of amyloidosis among patients with AS. Methods: A population-based cohort study was conducted comparing AS patients (n = 5911) with age-, sex- and ethnicity-matched control subjects (n = 29 007) with regard to incident cases of amyloidosis. Hazard ratios (HRs) and odds ratios (ORs) were estimated by Cox regression and logistic regression analyses, respectively. Results: The incidence rate of amyloidosis was 2.15 (95% CI 1.09, 2.82) and 0.35 (95% CI 0.16, 0.66) per 10 000 person-years among patients with AS and controls, respectively. The risk of incident amyloidosis was >6-fold higher among patients with AS relative to control subjects [adjusted HR 6.16 (95% CI 2.43, 15.62); P < 0.001]. A higher comorbidity burden [OR 1.36 (95% CI 1.08, 1.73); P = 0.010] was found to predict an increased susceptibility to amyloidosis in AS patients. Compared with other patients with AS, those with AS and comorbid amyloidosis had a 14-fold increased risk of end-stage renal disease necessitating dialysis [adjusted HR 14.7 (95% CI 2.0, 107.2); P = 0.008], but comparable risk of all-cause mortality [adjusted HR 2.16 (95% CI 0.69, 6.71); P = 0.174]. Conclusions: Patients with AS are at an increased risk of amyloidosis. AS-associated amyloidosis is associated with an elevated risk of dialysis dependence. Awareness of the burden and consequences of this complication may be of help for rheumatologists managing patients with AS.