Drug Resistance in Extrapulmonary Tuberculosis in Korea, 2010-2019: A Comparison With Pulmonary Tuberculosis

Background This study investigated drug resistance status and trends in patients with extrapulmonary tuberculosis (EPTB) and compared them with those in patients with pulmonary tuberculosis (PTB). Methods The phenotypic drug susceptibility test (DST) results of patients with culture-confirmed tuberculosis (TB) diagnosed at seven hospitals in South Korea between 2010 and 2019 were retrospectively analyzed. Results Overall, 10,557 patients were included in the analysis (747 and 9,810 patients in the EPTB and PTB groups, respectively). The proportion of EPTB among all patients with TB demonstrated an increasing trend over the study period. In the EPTB group, the pleura was the most commonly involved site (n = 246, 32.9%), followed by the lymph nodes (n = 152, 20.3%) and bones and joints (n = 138, 18.5%). Among 706 new patients with EPTB, the resistance rates to isoniazid (INH) and rifampicin (RIF) were 8.5% and 2.4%, respectively. The proportions of RIF-susceptible, INH-resistant TB, multidrug/rifampicin-resistant tuberculosis (MDR/RR-TB), and pre-extensively drug-resistant TB were 6.7%, 2.4%, and 0.7%, respectively. When comparing new patients in the EPTB group with those in the PTB group (8,607 patients), the resistance rates to RIF, ethambutol, and rifabutin and the proportion of MDR/RR-TB were significantly lower in the EPTB group. During the study period, the proportion of MDR/RR-TB among new patients showed a decreasing trend in both the EPTB and PTB groups. Conclusion This study provides important information on the resistance status and trends among patients with EPTB in South Korea. To improve the management of patients with EPTB, efforts to identify drug resistance and regular updates to the DST database are essential.