Prevalence of patients with self-reported hidradenitis suppurativa in a cohort of Danish blood donors: a cross-sectional study P. Theut Riis, O.B. Pedersen, V. Sigsgaard, C. Erikstrup, H.M. Paarup, K.R. Nielsen, K.S. Burgdorf, H. Hjalgrim, K. Rostgaard,K. Banasik, H. Ullum and G.B. Jemec Department of Dermatology, University Hospital Zealand, Sygehusvej 5, 4000 Roskilde, Denmark British Journal of Dermatology. DOI: 10.111/bjd.16079

Peter Theut Riis

Introduction What’s already known? • The population prevalence of hidradenitis suppurativa (HS) is estimated at between 1% and 4%. • It is suspected that patients with HS have a lower socioeconomic status. • Patients with HS are prone to depression and anxiety.

Objective To determine the prevalence of hidradenitis suppurativa in a cohort of Danish blood donors To compare donors with HS to donors without HS

Methods Hidradenitis Suppurativa can be diagnosed using questionnaire with a sensitivity of 90 % and a specificity of 97 %, a positive predictive value of 96 %, and a negative predictive value of 92 %.1 The diagnostic questions were included in a questionnaire presented to 27 625 Danish Blood donors 1. Vinding GR, Miller IM, Zarchi K et al. The prevalence of inverse recurrent suppuration: a population-based study of possible hidradenitis suppurativa. Br J Dermatol 2014; 170:884–9.

Methods The questionnaire contained the following items on: - Demographics (Height, weight) - Smoking habits - Alcohol consumption - Depression (Major depression inventory, MDI) - Life quality (Short Form – 12, PCS and MCS*) * Physical component summary and mental component summary

Methods The Unique civil registration number in Denmark allows for unambigious cross platform linkage of data from Statistics Denmark. We compared socioeconomic status and income of donors with HS to donors without. We explored how many of the donors with HS had a registered diagnosis of HS already.

Results The prevalence was 1.8 % (95% CI: 1.6 - 2.0%) Donors with HS had 1.3 kg/m2 higher BMI and more likely to be smokers (OR 1.44, 17.9% vs. 12.1%, P = 0.002).

Results Donors with HS were more likely to have moderate depression: (3.2% vs. 0.7%, P < 0.001) Donors with HS were less likely to drink wine (P = 0.02) but more likely to drink spirits and liquor. (P < 0.001)

Results Regression models showed that HS: - Increased MDI score by 1.427 (P < 0.001) - Did not affect SF-12 scores (PCS: P = 0.262, MCS: P = 0.067) - Did not affect salary (P = 0.968) - Did not affect total income (P = 0.596)

Results Rankable socioeconomic status Donors with HSa Donors without HSb P-value OR 1 Chief executive, n (%) 16 (3.2) 858 (3.2) 0.998 1.464 (95% CI 0.859–2.496) 2 High skill level employee, n (%) 77 (15.4) 4898 (18.3) 0.099 1.097 (95% CI 0.816–1.474) 3 Moderate skill level employee, n (%) 97 (19.4) 5500 (20.5) 0.537 1.136 (95% CI 0.862–1.497) 4 Basic skill level employee, n (%) 115 (23) 7030 (26.2) 0.103 Reference 5 Apprenticeship educated, n (%) 108 (21.6) 3874 (14.5) < 0.001* 1.484 (95% CI 1.043–2.113) 6 Unemployed, at least 6 months a year, n (%) 9 (1.8) 282 (1.1) 0.118 1.771 (95% CI 0.886–3.543) 7 Receiver of sickness benefits, educational support etc., n (%) 7 (1.4) 145 (0.5) 0.011 2.441 (95% CI 1.107–5.380) Table 3.  Socioeconomic status, and P-values for the difference between the groups. OR compared to strata 4 (Basic skill level employee)

Discussion Point prevalence of 1.8% (95% CI 1.64–1.96%) in healthy blood donors. Lower than population study of 2.2%,1 likely to reflect healthier source population (Blood donors), as HS is associated with smoking and being overweight. 1. Vinding GR, Miller IM, Zarchi K et al. The prevalence of inverse recurrent suppuration: a population-based study of possible hidradenitis suppurativa. Br J Dermatol 2014; 170:884–9.

Discussion Smoking and weight are increased in HS blood donors, but not as much as in HS patients indentified in population studies or recruited from hospitals. 1 1. Vinding GR, Miller IM, Zarchi K et al. The prevalence of inverse recurrent suppuration: a population-based study of possible hidradenitis suppurativa. Br J Dermatol 2014; 170:884–9.

Discussion HS donors earned less money in unadjusted analysis, but were younger. After correcting for age, BMI and sex, HS did not affect income.

Discussion HS donors had lower Socioeconomic status (SES), but not lower income, as previous suggested based on average household income for neigborhoods.2 2. J Am Acad Dermatol. 2016 Oct;75(4):755-759.e1. doi: 10.1016/j.jaad.2016.04.067. Epub 2016 Jul 21.

Discussion In line with previous studies, HS donors were more prone to depression. Only 2.2 % of donors with HS had their condition registered in the national patient database, suggested coding issues, a faulty screening tool or difficulty diagnosing mild disease. Previous study found 7.2 years from first symptoms to HS diagnosis.3 3) Br J Dermatol. 2015 Dec;173(6):1546-9. doi: 10.1111/bjd.14038. Epub 2015 Nov 3

Conclusions What does this study add? • The prevalence of HS in a population of Danish blood donors was estimated to be 1.8% (95% confidence interval 1.6–2.0%). • Blood donors with HS have a lower socioeconomic status based on job description, but HS does not seem to affect personal income, after adjusting for age and sex. • HS increases the risk of depression, even in a cohort of presumably mildly affected blood donors.

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