Retreatment after loss to follow-up reduces mortality in patients with multidrug/rifampicin-resistant tuberculosis

Background This study evaluated the risk factors of long-term mortality in patients with multidrug/ rifampicin-resistant tuberculosis (MDR/RR-TB) in South Korea who were lost to follow-up (LTFU). Methods This was a retrospective longitudinal follow-up study using an integrated database constructed by data linkage of the three national databases, which included 7226 cases of MDR/RR-TB notified between 2011 and 2017 in South Korea. Post-treatment outcomes of patients who were LTFU were compared with those of patients who achieved treatment success. Results Of the 7226 MDR/RR-TB cases, 730 (10.1%) were LTFU. During a median follow-up period of 4.2 years, 101 (13.8%) of the LTFU patients died: 25 deaths (3.4%) were TB related and 76 (10.4%) were non-TB related. In the LTFU group, the adjusted hazard ratio (aHR) of all-cause mortality (aHR 2.50, 95% CI 1.99-3.15, p<0.001), TB-related mortality (aHR 5.38, 95% CI 3.19-9.09, p<0.001) and non-TB-related mortality (HR 2.21, 95% CI 1.70-2.87, p<0.001) was significantly higher than that in the treatment success group. Independent risk factors for all-cause mortality in the LTFU group were age >55 years, fluoroquinolone resistance, cancer and no retreatment. In the LTFU patients who did not receive retreatment, the risk of non-TB-related mortality (aHR 5.00, 95% CI 1.53-16.37, p=0.008) and consequent all-cause mortality (aHR 2.18, 95% CI 1.08-4.40, p=0.030) was significantly higher than that of patients who received retreatment. Conclusion Non-TB-related mortality was the main cause of death and might be reduced by retreatment in LTFU patients with MDR/RR-TB.