A Study on the Relapse Rate of Tuberculosis and Related Factors in Korea Using Nationwide Tuberculosis Notification Data

OBJECTIVES From the perspective of public health, tuberculosis (TB) remains an important issue that threatens health. Korea is an intermediate burden country with a TB incidence of 97/100,000 individuals. Among many TB control measures, a relapse rate of TB is one indicator that can be used to indirectly assess the level of TB control in countries and in communities. Relapse TB has an approximately 12% yearly incidence in Korea. This study aims to estimate the relapse rate of TB and to investigate the associated factors by using nationwide TB notification data in Korea. METHODS The nationwide TB notification data in 2005 was used with the exclusion criteria of duplicated reporting, foreign-born patients, outcome-died, and outcome-diagnosis changed. The data were double-checked as to whether they were reported again during 2006-2010 and the estimated relapse rate of TB. Associated factors were analyzed by multivariate logistic regression with the variables of age, sex, registration type, results of sputum smear test, medication, and outcome of treatment. RESULTS Among 45,434 TB patients in 2005, 4,371 patients were again reported as TB patients from 2006 to 2010. Five hundred and sixty-four patients were reported more than twice and the cumulative number of relapses was 5,072 cases. The 5-year relapse rate was estimated as 9.62%. The relapse rate decreased yearly: 4.8% in 2006, 2.4% in 2007, 1.6% in 2008, 1.4% in 2009, and 1.0% in 2010. Age, sex, registration type, tuberculosis type, and medication were independently associated with a relapse of TB. In the multivariate logistic regression analysis, the following factors were related: male sex, 40-49 years old; registration type, relapse, treatment after failure, treatment after default, transfer in, and other, the sputum smear-positive pulmonary TB, and medications (including individuals taking 2-5 drugs). CONCLUSION This study has estimated a 5-year relapse rate of TB in Korea that is slightly lower than the rate of relapse TB in the annual reports. This study could be conducted and cross-checked with data from the National Health Insurance in the future.