[New criteria enable shorter hospitalization of patients with continuously smear-positive pulmonary tuberculosis].

BACKGROUND: Sputum conversion defined as 3 consecutive smear-negative sputum samples collected on different days is one of standard requirements for discontinuation of isolation for patients with smear-positive pulmonary tuberculosis (SPpTB). Sputum smear conversion is usually seen prior to culture conversion. However, in some patients, sputum smear tests are continuously positive for a long time. To discontinue isolation of the patients, culture conversion is required instead of smear conversion. Culture testing requires a long incubation period, which results in longer patient stay and isolation. OBJECTIVES: To identify a more efficient definition of culture conversion, which will enable treating physicians to take the decision to discontinue isolation. METHODS: The charts of patients with SPpTB admitted from September 2007 to March 2011 were reviewed. The recent definition of culture conversion is 3 subsequent culture-negative sputum specimens incubated for 6 weeks (3 CNs for 6 weeks) in liquid media. Treatment days and admission days were calculated based on the application of the new 3 definitions (3 CNs for 4 weeks, 2 CNs for 6 weeks, 2 CNs for 4 weeks). RESULTS: Of 301 patients, 224 were discharged after smear conversion; 77 were continuously smear-positive and were discharged after culture conversion. The median hospital stay was 56 days in patients discharged due to smear conversion and 107 days in patients discharged due to culture conversion, based on the recent definition. The numbers of treatment days needed for culture conversion were identical in most patients, regardless of definitions. At the time of reporting, all patients conformed to the new definitions and all the patients' sputum specimens were 3 CNs for 6 weeks except for one patient happened to be with 2 consecutive smear-negative specimens at an early phase of chemotherapy. The most efficient definition of culture conversion in this study was 2 CNs for 4 weeks. This enabled to shorten each patient's stay by 31 days and to lessen each patient's cost of hospitalization by about 4,900 dollars. CONCLUSION: Two subsequent CNs for 4 weeks of smear-positive sputum samples is enough to enable discontinuation of patient isolation and may thus shorten hospital stay.