Prevalence of patients with self-reported hidradenitis suppurativa in a cohort of Danish blood donors: a cross-sectional study

Background Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease characterized by recurrent inflamed nodules. No pathognomonic test is available for HS; hence the diagnosis is based on three clinical criteria. Objectives To estimate the cross-sectional prevalence and characterize patients with HS in the Danish Blood Donor Study cohort. Methods A questionnaire previously developed containing HS screening questions, the Major Depression Inventory, the Short Form-12, as well as questions about height, weight and drinking habits was answered by 27 765 blood donors. Results The prevalence of HS was 1 center dot 8% [95% confidence interval (CI) 1 center dot 6-2 center dot 0%] in the cohort of Danish blood donors. Donors with HS were on average 4 center dot 7 years younger (P < 0 center dot 001), had 1 center dot 3 kg m(-2) higher mean body mass index (BMI) (P < 0 center dot 001) and were significantly more likely to smoke [odds ratio (OR) 1 center dot 44, 17 center dot 9% vs. 13 center dot 1%, P = 0 center dot 002] compared with donors without HS. Furthermore, significantly more donors with HS were classified as having moderate depression (3 center dot 2% vs. 0 center dot 7%, P < 0 center dot 001). Also, significantly more patients with HS were apprenticeship educated, received educational support and sickness or cash benefits. Conclusions The prevalence of HS in the cohort of blood donors was estimated to 1 center dot 8% (95% CI 1 center dot 6-2 center dot 0%). Donors with HS reported characteristics similar to those reported for hospital-based patients with HS such as higher BMI, smoking rates and lower socioeconomic status than donors without HS.