Hidradenitis suppurativa (HS) has been associated with a high prevalence of spondyloarthritis; however, the population-based risk of developing inflammatory arthritis remains unclear.1 This population-based cohort study sought to evaluate the risk of developing inflammatory arthritis among patients with HS compared with matched patients without HS.
We used longitudinal claims data from commercially insured patients, including those with Medicaid and Medicare, covering 185 million lives in the United States between January 1, 2003, and January 1, 2016. We identified patients of all ages who received a diagnosis of HS (International Classification of Diseases, Ninth Revision code 705.83 or International Statistical Classification of Diseases and Related Health Problems, Tenth Revision code L73.2), defined as 1 diagnosis by a dermatologist or 3 diagnoses by any health care professional.2 The cohort entry date for the HS group was the first recorded diagnosis date of HS after at least 180 days of continuous enrollment (eFigure in the Supplement). For the non-HS group, we risk-set sampled 2 patients without HS from all plan enrollees who did not have a diagnosis of HS matched on the date the patient with HS entered the cohort. We excluded patients who had less than 180 days of continuous enrollment before cohort entry or had preexisting inflammatory arthritis, including ankylosing spondylitis, psoriatic arthritis, other spondyloarthritis, or rheumatoid arthritis (eAppendix in the Supplement). The Brigham and Women’s Hospital’s Institutional Review Board approved this study. All patient information was deidentified.