The Diagnostic Course of Sarcoidosis: A Population-Based Study Highlighting Risk Factors for a Delay in Diagnosis

Sarcoidosis is a systemic inflammatory syndrome of unknown cause characterized by granulomas, heterogeneous presentation, and variable clinical course. Diagnosis is often delayed, contributing to patient distress, increased healthcare costs, and potentially worse outcomes. Prior estimates of diagnostic delays rely largely on case-based studies, which may overestimate delays by failing to account for baseline care practices and common alternative diagnoses that may resemble sarcoidosis.

We conducted a retrospective population-based cohort study to characterize healthcare utilization before a sarcoidosis diagnosis and to identify risk factors associated with a diagnostic delay. Using longitudinal commercial, Medicare, and Medicaid healthcare insurance claims data from 2001-2022, we identified patients with sarcoidosis and evaluated diagnostic delay frequency, time to diagnosis, and potential missed opportunities for diagnosis. Secondary analysis compared diagnostic differences between pulmonary and cutaneous sarcoidosis.

87,092 sarcoidosis cases were identified, of which 56% experienced at least one healthcare visit with a symptomatically similar diagnosis before sarcoidosis was diagnosed. The mean time to diagnosis was 44 days, defined as the interval between increased baseline healthcare utilization and a sarcoidosis diagnosis. Patients had an average of 2.5 visits prior to sarcoidosis diagnosis that represented potential missed diagnostic opportunities. Pulmonary involvement was associated with longer time to diagnosis and more missed opportunities compared to cutaneous sarcoidosis. Risk factors for delays included obesity, outpatient evaluation, weekend visits, Medicaid insurance, and treatment for symptoms commonly attributable to sarcoidosis. Diagnosis was unaffected by age, season, or rural vs urban setting. Within Medicaid, white individuals had the highest risk for a missed diagnostic opportunity, while Black individuals had the lowest.

In this large population-based study, diagnostic delays in sarcoidosis were shorter than previously reported, yet substantial missed opportunities remain. Identifying patient- and system-level risk factors may help reduce delays, prevent disease progression, and improve outcomes in sarcoidosis.