Estimating the occurrence of renal complications among persons with ankylosing spondylitis.

Objective: The few published estimates of the risk of renal complications in ankylosing spondylitis (AS) are established on clinic-based studies. Our objective was to estimate the age- and sex-specific risks of renal complications in a population-based cohort of AS subjects in Québec between 1996 and 2006, relative to the general population.

Methods: A retrospective cohort design was implemented using population-based administrative data collected from 1996 to 2006 in Québec, Canada. The study cohort included subjects diagnosed with AS on physician billing records, and the comparison cohort comprised a 1% random sample of subjects without AS. Age- and sex-stratified prevalence ratios for acute kidney injury, chronic kidney disease, amyloidosis, and hypertensive renal disease were compared between subjects with and without AS.

Results: The AS cohort included 4,836 men and 3,780 women. Renal complications were diagnosed among 3.4% of men and 2.1% of women with AS compared with 2.0% and 1.6% of persons without AS, respectively. Renal complications were 72% more prevalent among persons with AS and an increase was observed in each of the conditions. The magnitude of the risk of renal complications was highest among younger individuals and decreased with advancing age.

Conclusion: These findings indicate that renal complications may be elevated among persons with AS, especially at younger ages. Despite the limitations of administrative data pertaining to onset of disease, these findings warrant further investigation because of their clinical relevance.