Behçet's syndrome epidemiology in England: a real-world retrospective cohort analysis with a nested case-control...

Behçet's syndrome (BS) is rare in the West. Using UK-linked primary and secondary care data we examine incidence, prevalence and clinical characteristics of this multisystem syndrome.

Clinical Practice Research Datalink (CPRD) Aurum and linked Hospital Episode Statistics (HES) enabled estimates of BS epidemiology using the earliest diagnosis code in CPRD or HES between 2001 and 2021. Median time from the first clinical code of a manifestation of interest to confirmed BS diagnosis was determined. A matched case-control design (CPRD Aurum) enabled ORs for BS for a variety of preselected covariates of interest to be calculated.

1565 incident BS cases arose in the study interval, translating to a final incidence rate of 0.75/100 000 person years at risk in 2021. Prevalence rose from 8.62 to 19.80 per 100 000 person years. In 1628 cases of BS in CPRD Aurum, matched with 11 190 controls, the triad of genital ulceration (adjusted OR (aOR) 155.08), uveitis (aOR 43.00) and oral ulceration (aOR 24.73) was significantly increased among participants with BS. ORs for Crohn's disease (5.69) were also higher in the BS cohort compared with controls. First appearance of the clinical code for genital ulceration was associated with the shortest interval to diagnosis (median 240 days; IQR 63-745).

BS prevalence appears to increase over time in the UK, potentially linked to changing population demographics and migration, and to performance characteristics of the 2014 International Criteria for Behçet's Disease classification criteria in low-prevalence settings. Recognised clinical characteristics and inflammatory conditions with phenotypical overlap were associated with BS. Diagnostic delay could be reduced by recognition of risk factors and differentiating clinical manifestations. Case ascertainment relied on diagnostic coding without direct validation against classification criteria, which is an important limitation.