Bidirectional association between tuberculosis and sarcoidosis

Background and objective Tuberculosis (TB) and sarcoidosis are both granulomatous diseases with potential interassociations. However, much uncertainty remains; thus, the present study aimed to clarify the association between these diseases. Methods We established two cohorts in this retrospective longitudinal cohort study using data obtained from the Taiwan National Health Insurance Database from 2000 to 2015. One cohort, which comprised 31 221 patients with TB and 62 442 age-, sex- and index year-matched controls, was used to analyse the risk of sarcoidosis; the other cohort comprised 2442 patients with sarcoidosis and 9688 controls and was used to assess the risk of TB. A Cox proportional hazards model adjusted for potential confounders was used in each cohort. Results Patients with TB showed an 8.09-fold higher risk of developing sarcoidosis than non-TB subjects (95% CI = 3.66-17.90), whereas patients with sarcoidosis showed a 1.85-fold higher risk of developing TB than non-sarcoidosis subjects (95% CI = 1.36-2.50). The TB subtype analysis revealed the highest risk of developing sarcoidosis in patients with extrapulmonary TB, and the highest risk of developing extrapulmonary TB was observed in patients with sarcoidosis compared with non-sarcoidosis subjects. Patients with TB showed a higher risk of developing sarcoidosis throughout the follow-up period, but patients with sarcoidosis only showed a higher risk of developing TB within the first year. Conclusion TB is a risk factor for developing sarcoidosis. The results of this bidirectional cohort study also highlight the clinical difficulty of diagnosing sarcoidosis and TB.