CBNAAT Assay Limitations

The Cartridge-based Nucleic Acid Amplification Test (CBNAAT) test has some limitations such as:

1. Bacterial load below the Limit of Detection (LOD ~ 130 CFU/ml) may result in a false-negative result.
2. Patients on an anti-TB regimen can still have positive results due to killed bacilli in the specimen and hence cannot be used for follow-up.
3. A positive test result does not necessarily indicate the presence of viable organisms. It is, however, presumptive for the presence of Mycobacterium tuberculosis (MTB) and Rifampicin (Rif) resistance.
4. MTB detection is dependent on the number of organisms present in the sample. Quality specimen collection and timely processing of the sample will minimize the errors.
5. Test results might be affected by anti-TB medication. Therefore, therapeutic success or failure cannot be assessed using this test, because DNA might persist following antimicrobial therapy.
6. Mutations or polymorphisms in primer or probe binding regions may affect the detection of new or unknown MDR or Rif-resistant strains, resulting in a false-negative result.
7. Any modification in sample processing may alter the performance of the test.
8. Results should be interpreted in conjunction with clinical data available to the clinician.

Video:  

CBNAAT Assay Limitations

Resources

• GenXpert Manual Version 4.7b.
• Cepheid Training Resource; Module 9: Troubleshooting, p13-20.