PLoS ONE (Jan 2014)

Culture conversion rate at 2 months of treatment according to diagnostic methods among patients with culture-positive pulmonary tuberculosis.

  • Ha Youn Lee,
  • Kyoung Ok Chae,
  • Chang Hoon Lee,
  • Sun Mi Choi,
  • Jinwoo Lee,
  • Young Sik Park,
  • Sang-Min Lee,
  • Chul-Gyu Yoo,
  • Young Whan Kim,
  • Sung Koo Han,
  • Jae-Joon Yim

DOI
https://doi.org/10.1371/journal.pone.0103768
Journal volume & issue
Vol. 9, no. 8
p. e103768

Abstract

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INTRODUCTION: The culture-negative conversion rate of sputum after 2 months of treatment in patients with pulmonary tuberculosis (TB) is used as a reliable surrogate marker for relapse after completion of treatment. We hypothesized that culture conversion of sputum at 2 months of anti-TB treatment and the time to culture conversion are different among pulmonary TB patients who are diagnosed using different methods. METHODS: Culture-confirmed pulmonary TB patients who were diagnosed between 1 January, 2011 and 31 December, 2012 were classified into three groups based on the diagnostic method that prompted treatment initiation: positive acid-fast bacilli (AFB) staining of sputum (smear-positive group), negative AFB staining, but Mycobacterium tuberculosis was cultured from sputum (culture-positive group), and positive AFB staining, positive polymerase chain reaction (PCR) for M. tuberculosis, or culture of M. tuberculosis from a bronchoscopic specimen (bronchoscopy group). Rates of negative mycobacterial culture conversion at 2 months of anti-TB treatment and the time to negative culture conversion of sputum were compared among the three groups. RESULTS: A total of 203 patients with culture-confirmed pulmonary TB were included in the final analysis. TB patients in the culture-positive group (94.1%) and the bronchoscopy group (97.6%) showed a higher culture conversion rate at 2 months of treatment than those in the smear-positive group (78.7%, P = 0.001). Additionally, the time to culture conversion was longer in the smear-positive group (median, 40 days) than in the culture-positive (median, 19 days; P = 0.009) and bronchoscopy groups (median, 29 days; P = 0.004). CONCLUSIONS: The higher culture conversion rate at 2 months and the shorter time to culture conversion among pulmonary TB patients with a negative AFB smear suggests the feasibility of shortening treatment duration and isolation in these patients.