Analysis of a simplified concentration sputum smear technique for pulmonary tuberculosis diagnosis in rural hospitals

Rural hospitals in Africa face the challenge of an increasing number of pulmonary tuberculosis (PTB) cases, much of it related with the AIDS pandemic. The main diagnostic tool in these hospitals is the direct sputum smears. Sensitivity of direct sputum smears is low, especially in cases of AIDS related PTB. Several concentration methods have been described but none is routinely used in Zimbabwe. Fluorescence microscopy of auramine stained samples increases sensitivity and saves laboratory time but it is not an appropriate technique for rural African hospitals. In a rural hospital of southwest Zimbabwe, we studied the sensitivity and appropriateness of a simplified concentration method. The sensitivity against culture was significantly higher with the concentration method (80%) than with the classical direct smear method (57%). However, when sputum is not adequate (with high number of squamous epithelial cells, meaning upper airway origin), the sensitivity of this method is low. A combination of both methods is proposed to increase the sensitivity of PTB diagnosis in rural hospitals.