Improved sensitivity of direct microscopy for acid-fast bacilli: sedimentation as an alternative to centrifugation for concentration of tubercle bacilli.

There is a great need for improved methods for the diagnosis of tuberculosis by techniques that are appropriate for control programs in low-income countries. Liquefaction of sputum with sodium hypochlorite followed by concentration of bacilli through overnight sedimentation significantly increases the sensitivity of direct microscopy, and this method could be an alternative for diagnostic centers not equipped with a centrifuge.