False Positive MGIT Cultures

False positives are test results reported as positive for a Mycobacterium species not present in the patient specimen. 

1. Not all false positives are due to laboratory cross-contamination.

2.  All laboratories are capable of producing false positive results.

Practices that can lead to false positive cultures are:

1. Inadequate sterilization of instruments such as bronchoscopes

2. Mislabeling at the time of collection or time of accessioning

3. Use of contaminated water for specimen collection or laboratory procedures

4. Shared reagents and dispensers

5. Opening more than one specimen container at a time while processing

6. Mix-up of testing samples or lids

7. Failure to take precautions to minimize aerosol production

Resource

Mycobacterial Culture

Assessment