Association of Underlying Comorbidities and Sites of tuberculosis: an analysis using surveillance data

Background: Tuberculosis (TB) is a highly heterogeneous disease that can affect any organ. Extrapulmonary TB (EPTB) is more difficult to diagnose due to various clinical presentations. Depending on the characteristics of the patient, the involved site of TB may vary. However, data on clinical characteristics of EPTB are inconsistent and insufficient. This study aimed to identify the characteristics of patients with pulmonary TB (PTB) and EPTB and describe characteristic differences for each involved site. Methods: We systemically collected data of TB patients included in the national surveillance system in South Korea from July 2018 to June 2019 and compared the characteristics of patients with EPTB with that of PTB. Results: A total of 7674 patients with a mean age of 60.9 years were included. Among them, 6038 (78.7%) patients were diagnosed with PTB and 1636 (21.3%) with EPTB. In PTB group, the mean age (61.7 ± 18.7 vs. 57.8 ± 19.9) and proportion of male sex (63.3% vs. 50.1%) were higher, but the body mass index was lower (21.2 ± 3.4 vs. 22.7 ± 3.5) than that of the EPTB group. Prevalence of diabetes (20.5% vs. 16.9%) and chronic lung disease (5.1% vs. 2.9%) were higher in PTB group, meanwhile, those of chronic kidney disease (CKD) (2.7% vs. 5.4%) and long-term steroid use (0.4% vs. 1.0%) were higher in EPTB group. Abdominal TB was more prevalent in patients with chronic liver disease (odds ratio [OR]: 2.69, 95% CI: 1.52–4.74), and urogenital TB was more prevalent in patients with CKD (OR: 2.75, 95% CI: 1.08–6.99). Conclusions: We found that underlying comorbidities were closely associated with the location of TB development, and therefore, the possibility of EPTB should be carefully evaluated while monitoring for underlying disease in TB-endemic areas.