Sputum smear positivity at two months in previously untreated pulmonary tuberculosis patients

In pulmonary tuberculosis, bacteriological status at two months affects subsequent treatment and prognosis. The effect on treatment outcome and risk factors for sputum conversion at two months treatment in previously untreated pulmonary tuberculosis (PTB) patients was studied in the following report.

A 1:1 case-control study was performed from June 2006 to February 2008 on patients in the Revised National Tuberculosis Control Program in a tertiary level institute in Delhi, India. Patients with previously untreated PTB with sputum smear positive at 2months of treatment (cases) were compared with those who achieved conversion (controls).

In 74 cases and 74 controls, independent risk factors for sputum smear positive at two months were: illness for >2months, presence of cavity or extensive disease on chest X-ray, and interruption in intensive phase of treatment. Patients with smear positive at 2 or 3months of treatment were more likely to fail or default from treatment. Aforesaid factors were also associated with sputum culture positive status at 2months in univariate analysis. Patients who interrupted treatment ⩾3 times in the first two months were more likely to be culture positive at two months and had a higher rate of default and failure.

Illness for more than 2months, presence of cavity or extensive disease on chest X-ray, and interruption in intensive phase of treatment are independent risk factors for sputum smear positivity at two months, which in turn is associated with poor treatment outcomes. Patients with these factors merit special attention under the national program.