Multiple misdiagnoses of tuberculosis resulting from laboratory error--Wisconsin, 1996.

A positive culture for Mycobacterium tuberculosis confirms a diagnosis of tuberculosis disease (TB); however, false-positive cultures have resulted from laboratory error. In 1996, the Division of Health (DOH), Wisconsin Department of Health and Family Services, became aware of five possible incidents of laboratory error associated with the processing of M. tuberculosis cultures; these incidents resulted in the potential misdiagnosis of TB in 11 persons. This report summarizes the findings from the investigation of the five incidents, which suggest that four incidents were associated with cross-contamination of specimens in the laboratory and one with the inadvertent inoculation of a subculture from the incorrect broth medium; these errors resulted in adverse effects on patients and on the medical and public health systems.