Prevalence of hidradenitis suppurativa in a Turkish population: validation of a screening questionnaire in Istanbul, Turkey

Hidradenitis suppurativa (HS) is a chronic inflammatory condition involving abscesses, sinus tracts, and scarring, primarily in intertriginous areas. Emerging typically in the third and fourth decades, HS often leads to significant emotional distress due to stigmatization, reducing the quality of life. The prevalence of HS varies across populations and study designs (0.00033–4.1%).1 However, epidemiologic HS studies from Turkey are lacking. This study investigates the prevalence of HS in Istanbul, Turkey, validates the HS screening questionnaire, and contributes to the Global Hidradenitis Suppurativa Atlas (GHiSA). This cross-sectional, single-center study included 550 healthy adults at Koç University Hospital, Istanbul, Turkey, between July 2023 and January 2024. The study followed the GHiSA initiative's objective, methods, and approach.1 Participants were randomly recruited from healthy adults accompanying patients to various outpatient or inpatient services, excluding the dermatology department. Verbal and written informed consent were obtained. Those who did not consent to participate in the study, pregnant women, and persons who were not able to consent (unconscious persons, persons younger than 18 years of age, and psychiatric patients) were excluded. The questionnaire was translated into Turkish, and medical students performed data collection. A dermatologist confirmed the diagnosis in patients with positive responses. Additionally, 10% of randomly selected negatively screened participants were clinically examined. Severity was categorized using the Hurley scoring system. Out of 688 healthy adults that were approached, 138 were excluded due to various reasons (Figure 1). The HS prevalence in the remaining 550 participants was 1.27% (95% CI 0.95: 0.62%–2.60%). The participants comprised 366 females and 184 males, with a median age of 34 years (IQR 26–47) in the control group and 29 (IQR 27.5–36.5) years in the HS group (Table 1). Seven participants were diagnosed with HS, predominantly affecting the axilla (71.4%), followed by anogenital area (29%) and inframammary folds (14%). Hurley I was seen in six patients, while one patient had Hurley II. The median body mass index (BMI) was similar between the HS and control groups, but smoking was significantly more common in HS patients (85.7% vs. 37.38%, P = 0.0137). No significant difference was observed in gender (P = 0.6916), age (P = 0.4896), and BMI (P = 0.4896) between the HS and control groups (Table 1). The screening questionnaire had a sensitivity of 1 (7/7), a specificity of 0.89 (55/62), a positive predictive value of 0.50 (7/14), and a negative predictive value of 1 (55/55). Among the 543 participants who screened negative, 55 were randomly selected for clinical evaluation, and all confirmed negative. The prevalence of HS in Istanbul aligns with its global prevalence rates. Other studies using the same validated questionnaire report a prevalence of 2.2% in Nigeria,2 0.67% in Ghana3 and Australia,4 and 0.59% in Singapore.5 No gender predominance was observed in the HS group. The HS cases in this study are milder in severity, likely due to the screening of healthy adults in a non-dermatology setting. As most patient companions were female, the majority of participants were female. The screening questionnaire demonstrated high sensitivity and specificity, making it efficient for screening large populations. However, dermatological exams are crucial for confirming positive cases, as symptoms can resemble conditions such as acne and folliculitis, potentially leading to false positives. This study also contributed to GHiSA, enhancing the understanding of HS prevalence globally. Verbal and written informed consent were obtained prior to study participation. The data supporting this study's findings are available from the corresponding author upon reasonable request.