Influence of pre-treatment bacillary load on treatment outcome of pulmonary tuberculosis patients receiving DOTS under revised national tuberculosis control programme.

OBJECTIVE: To study the influence of initial bacillary load on sputum conversion rates and treatment outcome of new smear positive pulmonary tuberculosis patients.
METHODS: A retrospective study was done among 2938 new smear positive pulmonary tuberculosis patients, registered at the peripheral centres, covering a population of 1.6 million in Delhi, India. The patients pre-treatment sputum smears were graded as 1+, 2+ or 3+ based on three samples. Patients were given intermittent short-course chemotherapy under supervision and the treatment outcome was analysed.
RESULTS: Sputum conversion rates among patients graded as sputum 3+ and rest of the patients (combined graded sputum 1+ and 2+) at the end of two months were 62.2% and 76.8% respectively (p<0.001), and at the end of three months were 81.3% and 89.5% respectively (p<0.001). Cure rates among same group of patients were 76.6% and 85.1% respectively (p<0.001), and failure rates were 7.7% and 4.5% respectively (p<0.001).
CONCLUSIONS: Under field conditions even with directly observed treatment (DOT) new smear positive patients with heavy bacillary load showed statistically significant poor sputum conversion rates at two and three months and higher failure rates as compared to patients with lesser bacillary load. To investigate possible reasons for this poor response and possible solutions further studies are needed.