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March 19, 1997

Laboratory Errors and the Misdiagnosis of Tuberculosis-Reply

Author Affiliations

Tuberculosis Control Program Los Angeles County Department of Health Services Los Angeles, Calif

JAMA. 1997;277(11):883. doi:10.1001/jama.1997.03540350033022

In Reply.  —The laboratory procedure instituted by Dr Kaye and colleagues is an excellent response to the problem of misdiagnosis of TB due to laboratory contamination. Recently, Frieden et al1 reported that 12 (2.7%) of the 441 patients in New York City whose specimens grew M tuberculosis in April 1991 had false-positive cultures due to crosscontamination in the laboratory. The laboratory procedure described by Kaye et al, which includes medical record review for clinical correlation, is especially important in light of these findings.The mycobacteriology section of the Public Health Laboratory in Los Angeles County has also instituted measures to prevent cross-contamination. Single-use containers to dispense processing reagents are kept outside of the biological safety cabinet and are only brought into the cabinet for immediate dispensing. Procedures to limit aerosol generation also have been instituted, including avoiding removing specimen container caps and stoppers until enough time has passed to allow settling