S. Jenkins-Jones, V. Piguet, J.R. Ingram, D.W. Knipe, R. Cannings-John, C.L.I. Morgan
Epidemiology data regarding hidradenitis suppurativa (HS) are conflicting and prevalence estimates vary 80-fold, from 0.05% in a population-based study, to 4%.
To assess the hypothesis that previous population-based studies under-estimated true HS prevalence by missing undiagnosed cases.
We performed a population-based observational and case-control study using the UK Clinical Practice Research Datalink (CPRD) linked to Hospital Episode Statistics data. Physician-diagnosed cases in CPRD were identified from specific Read codes. Algorithms identified unrecognised ‘proxy’ cases, with at least five Read code records for boils in flexural skin sites. Validation of proxy cases was undertaken with General Practitioner questionnaires to confirm criteria-diagnosed cases. A case-control study assessed disease associations.
On 30 June 2013, 23,353 physician-diagnosed HS cases were documented in 4,364,308 research-standard records. 68,890 proxy cases were identified, reduced to 10,146 criteria-diagnosed cases after validation, extrapolated from 107 completed questionnaires (61% return rate). Overall point prevalence was 0.77% (95% CI 0.76% to 0.78%). An additional 18,417 cases had a history of 1-4 flexural skin boils.
In physician-diagnosed cases, ORs for current smoker and obesity (BMI>30) were 3.61 (95% CI 3.44 to 3.79) and 3.29 (95% CI 3.14 to 3.45). HS was associated with type 2 diabetes, Crohn's disease, hyperlipidaemia, acne and depression and not associated with ulcerative colitis or polycystic ovary syndrome.
Contrary to results of previous population-based studies, HS is relatively common, with a UK prevalence of 0.77%, one-third being unrecognised, criteria-diagnosed cases using the most stringent disease definition. If probable cases are included, HS prevalence rises to 1.19%.
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