Abstract

Aim : The aim of the study is to investigate the clinical significance of low serum isoniazid level among the patients with drug-sensitive pulmonary tuberculosis who showed delayed smear or culture conversionMethods : Medical records of patients with pulmonary tuberculosis who underwent protocol-based treatment were reviewed. Drug level monitoring was done for who showed delayed sputum smear or culture conversion beyond 2 months, and who showed negative conversion within 2 months but positive re-conversion beyond 2 months. Primary endpoint was treatment failure, which was defined as a case with positive sputum culture beyond 4 months. Results : Total 50 patients were included. 27 patients composed treatment failure group, and 23 patients comprised conversion group. In a multivariable logistic regression model, serum isoniazid level was inversely related with treatment failure (adjusted OR=0.30, p=0.20), after adjusting BMI and rifampin dose. In a Classification And Regression Tree (CART) model, low serum isoniazid level(below 2.55 ?/ml) was the most important variable for predicting treatment failure, whereas high BMI (more than 22.59 kg/m2) was related with treatment failure.Conclusions : Low serum isoniazid level was related with treatment failure among the patients with drug-sensitive pulmonary tuberculosis who showed delayed smear or culture conversion.Further studies which investigate whether increasing dose of isoniazid among the whose isoniazid level is low would improve clinical outcome are needed.