Yield of continued monthly sputum evaluation among tuberculosis patients after culture conversion

New York City.

To evaluate the yield of continued monthly sputum monitoring after culture conversion.

A retrospective review of tuberculosis patients verified between 1 January 1995 and 31 December 1996 who had: 1) pulmonary tuberculosis with organisms susceptible to isoniazid and rifampin; 2) culture conversion; and 3) completed therapy. We assessed time to smear and culture conversion and number of persons who developed a positive culture after culture conversion (culture reversion).

Of 1440 patients, 379 were cared for by tuberculosis control program providers and 1061 were cared for by other providers; 813 (56%) were initially smear-positive. After the fifth month, 44 (5.3%) were smear-positive; four of these were culture-positive. Eighteen (1.3%) had culture reversions; eight were smear-positive. Excluding one specimen per patient collected at treatment completion, 7967 sputum samples were collected after culture conversion. The minimum estimated cost per culture reversion detected was $26,557.

Continued monthly monitoring of sputum after culture conversion identified a very small number of patients who had culture reversion. However, patients who cannot tolerate or adhere to a standard regimen may need continued monitoring to assess response to treatment. For all patients a specimen should be collected at the end of treatment to document cure.