The definition of past tuberculosis affects the magnitude of association between pulmonary tuberculosis and respiratory dysfunction: Korea national health and nutrition examination survey, 2008-2012

Tuberculosis (TB) is associated with an increased risk of chronic lung impairment. The aim of this study was to compare the clinical characteristics and lung functions according to definition of past TB. We used the population-based, Korea National Health and Nutrition Examination Survey (KNHANES) (2008-2012) to analyze 13,522 subjects age 40 years or older who underwent spirometry and chest X-ray (CXR). Subjects with TB lesions on CXR (with or without a history of TB) were older, more likely to be male, ever smokers, and of low socioeconomic status than subjects with only a history of TB or without evidence of TB. Airflow obstruction (AFO) was associated with only a history of TB (odds ratio [OR] 1.53, 95% confidence interval [CI] 0.95-2.46), only TB lesion on CXR (OR 2.37, 95% CI 1.80-3.12), and both a history and TB lesions on CXR (OR 4.47, 95% CI 3.07-6.51) after adjustment for gender, age, body mass index, education, income, and smoking amount (P for trend < 0.001). Spirometric restriction was associated with only a history of TB (OR 1.29, 95% CI 0.80-2.08), only TB lesions on CXR (OR 2.03, 95% CI 1.49-2.76), and both a history and TB lesions on CXR (OR 2.65, 95% CI 1.74-4.05) after adjustment for the above variables (P for trend < 0.001). How to define past TB in population study affects the magnitude of association between past TB and respiratory dysfunction. Without considering TB lesions on CXR, the association between TB and respiratory dysfunction could be underestimated.