Difference Between TrueNat and CBNAAT for Tuberculosis Diagnosis
TrueNat is an improvement over CBNAAT (GeneXpert) as it overcomes the limitations that restrict GeneXpert's decentralization to peripheral laboratories, making TrueNat more suitable for resource-limited settings while maintaining comparable diagnostic accuracy. 1
Key Differences Between TrueNat and CBNAAT
Technology and Platform
- CBNAAT (GeneXpert) uses cartridge-based technology where samples are transferred into testing cartridges loaded into the Gene-Xpert equipment for automated purification, extraction, and amplification of genetic material 1
- TrueNat uses chip-based real-time PCR technology where purified RNA is mixed with freeze-dried PCR reagents and dispensed into reaction wells of TrueNat chips inserted into a Truelab real-time micro PCR analyzer 1
Infrastructure Requirements
- CBNAAT requires continuous power supply, waste disposal system for cartridges, biosafety level 2 conditions, and trained laboratory staff 1
- TrueNat has minimal biosafety requirements as samples are collected in viral lysis medium, making it more suitable for peripheral laboratories with limited infrastructure 1, 2
Testing Capacity and Time
- CBNAAT can test up to 80 samples at a time depending on the number of test modules available, with a turnaround time of 30-45 minutes 1
- TrueNat can test 1-4 samples at a time depending on the module configuration, with a turnaround time of 35-50 minutes 1
Cost and Accessibility
- TrueNat has been proven more cost-effective than smear microscopy or Xpert for tuberculosis diagnosis 1
- TrueNat is designed as a portable, point-of-care test suitable for primary healthcare facilities in resource-limited settings 2, 3
Diagnostic Performance
Sensitivity and Specificity
- CBNAAT has approximately 62% sensitivity for detecting TB in cerebrospinal fluid with excellent specificity at approximately 98% 4
- TrueNat MTB Plus shows overall sensitivity of 90% (95% CI: 73.4-97.8) and specificity of 98.2% (95% CI: 96-99.3) for pulmonary TB detection 5
- For extrapulmonary TB, TrueNat MTB Plus demonstrates sensitivity of 81.8% (95% CI: 59.7-94.8) and specificity of 97.4% (95% CI: 95.1-98.8) 5
Concordance with Other Methods
- High concordance has been observed between GeneXpert and TrueNat for TB case detection 3
- When compared to GeneXpert, TrueNat MTB shows 90.5% sensitivity while TrueNat MTB Plus shows 100% sensitivity 6
Clinical Applications
Pulmonary TB Diagnosis
- Both CBNAAT and TrueNat provide results within 24-48 hours compared to culture which takes 2-6 weeks 4, 7
- Both can detect M. tuberculosis bacteria weeks earlier than culture for 80-90% of patients whose TB is ultimately confirmed by culture 4
Extrapulmonary TB Diagnosis
- CBNAAT has been endorsed by the WHO as the screening test for diagnosing extrapulmonary tuberculosis 8
- TrueNat has shown good diagnostic accuracy for both pulmonary and extrapulmonary TB detection 5
Drug Resistance Detection
- CBNAAT simultaneously detects rifampicin resistance along with M. tuberculosis in less than 3 hours 3
- TrueNat also offers rifampicin resistance detection capabilities through its MTB-RIF Dx assay 6
Common Pitfalls and Considerations
- Neither test should be used as the sole diagnostic tool; culture remains important for definitive diagnosis, especially in extrapulmonary TB 8
- A negative result from either CBNAAT or TrueNat does not exclude TB, particularly in paucibacillary cases like TB meningitis 4
- Both tests may miss non-tuberculous mycobacteria that can be detected by microscopy techniques 7
Practical Implementation
- TrueNat is particularly valuable in resource-limited settings where continuous power supply and advanced laboratory infrastructure are not available 1, 2
- CBNAAT may be more suitable for higher-volume testing centers with appropriate infrastructure 1
- Both technologies significantly improve TB diagnostic capabilities compared to conventional microscopy methods 7, 3