New prevalence estimates for hidradenitis suppurativa in the United States

1. In a population-based analysis of over 48 million records in the United States (US), the overall prevalence of hidradenitis suppurative (HS) was 0.10%.

2. The prevalence was highest among women, African American and biracial patients, and patients 18-49 years-old.

Evidence Rating Level: 3 (Average)

Study Rundown: HS is a chronic, inflammatory skin disease that primarily affects the intertriginous areas and presents as painful nodules that progress to abscesses, sinus tracts, and scarring. Prevalence estimates of HS vary considerably with reports ranging from 0.00033% to 4.1%. However, these estimates are based on small study populations sourced from claims analyses, retrospective chart reviews, or patient questionnaires. Few large standardized population-based studies with validated search strategies have been performed. Thus, the true overall prevalence of HS is unknown. The objective of this study was to elucidate the prevalence of HS in the US overall and for specific demographics.

The study retrospectively performed an adjusted population analysis using a case cohort of over 48 million patients sourced from a multi-institutional data analytics and research platform to determine the prevalence of HS in the US.  At the conclusion of the study, 47,690 patients with HS were identified, demonstrating a point prevalence of 0.10%. Moreover, prevalence was greater for females, patients 18-49 years old, and African American and biracial patients. The results of this study indicate that HS is uncommon but not rare, and thus, there are significant healthcare burdens and costs associated with the disorder. Strengths of this study include the use of a large, diverse cohort sourced from many healthcare organizations across the US, use of a platform validated through other epidemiology studies, and the use of standardized vocabulary and classification systems. Limitations of the study include excluding patients that may have HS but were never diagnosed, assuming that the HS diagnosis was made by experienced clinicians, and excluding patients that were not seen at the participating healthcare institutions. Future prospective cohort studies where HS is diagnosed by a trained health professional will help better establish the true prevalence of HS.

Click to read the study in JAMA Dermatology

Relevant Reading: Analysis of patient claims data to determine the prevalence of hidradenitis suppurativa in the United States

In-Depth [retrospective cohort]: This study retrospectively evaluated the prevalence of HS in the United States in the overall population and for specific demographics. Overall, the study cohort included over 48 million patients from 27 healthcare organizations across the US from 1999 to 2016. Patients with HS were identified using International Classification of Disease (ICD-9) codes with a previously validated case identification method that demonstrated a positive predictive value of 77%. Confidence intervals were calculated using the Wilson score method and gamma distribution. There were 47,690 patients with HS identified with point prevalence of 0.10% (95%CI: 97-99 per 100 000 persons). Prevalence in females (137 per 100,000; 95%CI: 136-139 per 100,000) was two-fold greater than men (58 per 100,000; 95%CI: 57-59 per 100,000; p< 0.001). Prevalence of HS in African American and biracial patients were 296 per 100 000 (95% CI: 291-300 per 100 000) and 218 per 100 000 (95%CI: 202-235 per 100 000), respectively. Among all age groups, the prevalence of HS in patients ages 30-39 years old was greatest (172 per 100,000; 95%CI: 169-175 per 100,000).

Image: CC/Wiki/Samuel Freire da Silva

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