Review of false-positive cultures for Mycobacterium tuberculosis and recommendations for avoiding unnecessary treatment

We reviewed reports of false-positive cultures for Mycobacterium tuberculos is and here propose guidelines for detecting and managing patients with pos sible false-positive cultures. Mechanisms of false-positive cultures includ ed contamination of clinical devices, clerical errors, and laboratory cross -contamination. False-positive cultures were identified in 13 (93%) of the 14 studies that evaluated greater than or equal to 100 patients; the median false-positive rate was 3.1% (interquartile range, 2.2%-10.5%). Of the 236 patients with false-positive cultures reported in sufficient detail, 158 ( 67%) were treated, some of whom had toxicity from therapy, as well as unnec essary hospitalizations, tests, and contact investigations. Having a single positive culture was a sensitive but nonspecific criterion for detecting f alse-positive cultures. False-positive cultures for M. tuberculosis are not rare but are infrequently recognized by laboratory and clinical personnel. Laboratories and tuberculosis control programs should develop procedures t o identify patients having only 1 positive culture. Such patients should be further evaluated for the possibility of a false-positive culture.