Value of third sputum smear for detection of pulmonary tuberculosis in HIV infected patients

We evaluated diagnostic yield of third sputum smear in patients co infected with HIV for detection of pulmonary tuberculosis. Among 139 pulmonary tuberculosis cases confirmed with positive sputum culture, diagnostic yield of first smear of sputum with acid fast staining was 83.5%. Incremental yield of 2nd and 3rd samples was 11.2% and 5.2% respectively. So two sputum smears may be enough for primary evaluation of HIV infected patients suspected to TB.