Supplementary Material for: Prevalence of Hidradenitis Suppurativa in an African population: Validation of a screening questionnaire in Lagos, Nigeria

Background: Epidemiologic Hidradenitis Suppurativa (HS) studies from Africa are lacking. This study aimed at uncovering the prevalence of HS in Lagos, Nigeria, validate an HS screening questionnaire, and to contribute to the Global Hidradenitis Suppurativa Atlas (GHiSA). Methods: This was a cross-sectional study of 802 healthy adults accompanying their relations to the outpatient clinic of Family Medicine and Ophthalmology at the Lagos State University Teaching Hospital in Lagos, Nigeria following ethical approval. Verbal and written consent were obtained prior to inclusion of study participants. The study was conducted using a validated screening questionnaire. Screen positive and randomly selected screen negative participants were clinically examined. Severity was categorized using the Hurley Score. Results: The prevalence of HS in the sample was 2.2% (18/802; 95% CI:1.4% - 3.5%) with no gender predominance. The mean age in the HS group was 34 years (IQR 28-42), and the median BMI of the HS patients was 27.0 (IQR 21.4-28.6). There was no significant difference in BMI between the HS and control group. The screening questionnaire had a sensitivity of 1 (18/18), specificity of 0.8 (20/25), positive predictive value of 0.8 (18/23), and a negative predictive value of 1 (20/20). The axilla was the predominant site of affection (66.7%), and all HS patients were classified as mild disease (Hurley Score I). Conclusion: The prevalence of HS in Lagos, Nigeria was 2.2% and, in this population, BMI did not appear to be a risk factor. The axilla was the most affected site, and all patients had a mild disease severity (Hurley Score I). Finally, the HS screening questionnaire is a suitable tool in population surveys.