A Prospective, Multicenter Study
A Prospective, Multicenter Study
A prospective study of false-positive cultures of Mycobacterium tuberculosis that resulted from laboratory cross-contamination was conducted at three laboratories in California. Laboratory cross-contamination accounted for 2% of the positive cultures. Cross-contamination should be a concern when an isolate matches the genotype of another sample processed during the same period.
Culture remains the reference standard for diagnosis of disease caused by Mycobacterium tuberculosis. However, false-positive results can be caused by cross-contamination of cultures in the laboratory, e.g., when M. tuberculosis bacilli are transferred from one specimen to another specimen that does not contain viable bacilli. Historically, determining whether false-positive results are caused by laboratory cross-contamination has been difficult because of the lack of specific strain identification and nonsystematic criteria. False-positive cultures for M. tuberculosis have important implications for clinical management of patients. Many patients are treated on the basis of the results; therefore, patients can be exposed to unnecessary, potentially toxic, and costly treatment. Genotyping of M. tuberculosis strains has become the standard method for determining whether isolates are clonal. This technique, in combination with a review of clinical and radiographic data, allows a determination of the incidence of laboratory cross-contamination of M. tuberculosis cultures. In this study, we used predefined criteria to investigate possible laboratory cross-contamination of M. tuberculosis cultures and prospectively determine its incidence in an effort to find methods to decrease the occurrence of cross-contamination.
A prospective study of false-positive cultures of Mycobacterium tuberculosis that resulted from laboratory cross-contamination was conducted at three laboratories in California. Laboratory cross-contamination accounted for 2% of the positive cultures. Cross-contamination should be a concern when an isolate matches the genotype of another sample processed during the same period.
Culture remains the reference standard for diagnosis of disease caused by Mycobacterium tuberculosis. However, false-positive results can be caused by cross-contamination of cultures in the laboratory, e.g., when M. tuberculosis bacilli are transferred from one specimen to another specimen that does not contain viable bacilli. Historically, determining whether false-positive results are caused by laboratory cross-contamination has been difficult because of the lack of specific strain identification and nonsystematic criteria. False-positive cultures for M. tuberculosis have important implications for clinical management of patients. Many patients are treated on the basis of the results; therefore, patients can be exposed to unnecessary, potentially toxic, and costly treatment. Genotyping of M. tuberculosis strains has become the standard method for determining whether isolates are clonal. This technique, in combination with a review of clinical and radiographic data, allows a determination of the incidence of laboratory cross-contamination of M. tuberculosis cultures. In this study, we used predefined criteria to investigate possible laboratory cross-contamination of M. tuberculosis cultures and prospectively determine its incidence in an effort to find methods to decrease the occurrence of cross-contamination.