AFB-DNA (TB-PCR) Detection by RTPCR, Reflex to Rifampicin resistance by Ultra CBNAAT (Specimen)
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No Fasting Required
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AFB-DNA (TB-PCR) Detection by RTPCR Reflex to Rifampicin resistance by Ultra CBNAAT
- Why is it done?
- Detection of Mycobacterium tuberculosis (MTB) DNA using Real-Time PCR technology to confirm active tuberculosis infection
- Simultaneous identification of rifampicin resistance mutations using Ultra CBNAAT (Cartridge Based Nucleic Acid Amplification Test) as a reflex test
- Rapid diagnosis of TB in patients with respiratory symptoms (cough, fever, night sweats, weight loss)
- Early detection of drug-resistant tuberculosis (MDR-TB) to guide appropriate treatment protocols
- Confirmation of TB diagnosis in patients with positive sputum smear microscopy or clinical suspicion
- Initial diagnostic testing for patients with suspected TB, including those with HIV co-infection
- Monitoring treatment response and detection of treatment failure or relapse
- Normal Range
- MTB DNA Detection: NEGATIVE (NOT DETECTED) - indicates no tuberculosis DNA detected in the specimen
- Rifampicin Resistance: NOT DETECTED - indicates susceptibility to rifampicin (drug-sensitive TB)
- Interpretation of Results:
- NEGATIVE: No MTB DNA detected - patient does not have active TB infection; normal finding
- POSITIVE: MTB DNA detected with Rifampicin SUSCEPTIBLE - patient has drug-sensitive TB
- POSITIVE: MTB DNA detected with Rifampicin RESISTANT - patient has MDR-TB (Multi-Drug Resistant TB)
- INCONCLUSIVE/ERROR: Test failed to produce clear results; specimen may require re-collection or repeat testing
- Interpretation
- MTB DNA NEGATIVE:
- No evidence of active tuberculosis infection
- Rules out TB as the cause of respiratory symptoms; consider alternative diagnoses
- Note: Negative result does not exclude TB if clinical suspicion remains high; repeat testing may be warranted
- MTB DNA POSITIVE with Rifampicin SUSCEPTIBLE:
- Confirms diagnosis of active tuberculosis
- Indicates susceptibility to rifampicin - patient can be treated with standard first-line anti-TB drugs
- Standard TB regimen recommended (Isoniazid, Rifampicin, Pyrazinamide, Ethambutol)
- MTB DNA POSITIVE with Rifampicin RESISTANT:
- Confirms diagnosis of Multi-Drug Resistant TB (MDR-TB) - resistance to both isoniazid and rifampicin
- Requires modification of treatment regimen to include second-line anti-TB drugs
- Treatment typically includes fluoroquinolones, injectable agents, and bedaquiline or linezolid
- Associated with longer treatment duration and higher risk of treatment failure
- Factors Affecting Test Accuracy:
- Specimen quality and type (sputum, bronchoalveolar lavage, cerebrospinal fluid)
- Bacterial load in specimen - higher bacillary load increases sensitivity
- Stage of TB infection - sensitivity lower in early disease
- HIV co-infection status - may affect bacillary load and test performance
- Presence of inhibitors in specimen that may affect PCR amplification
- Associated Organs
- Primary Organ Systems:
- Respiratory System (Lungs) - primary site of infection in pulmonary TB
- Immune System - TB affects macrophages and CD4+ T cells
- Medical Conditions Associated with Abnormal Results:
- Pulmonary Tuberculosis (PTB) - most common form affecting lungs
- Extrapulmonary Tuberculosis (EPTB) - TB affecting other organs including lymph nodes, pleura, meninges, bones
- Multi-Drug Resistant TB (MDR-TB) - TB resistant to isoniazid and rifampicin
- Extensively Drug-Resistant TB (XDR-TB) - resistance to fluoroquinolones and injectable drugs
- TB-HIV co-infection - patients with HIV have higher TB risk
- Potential Complications of Abnormal Results:
- Cavitary lung disease with potential hemoptysis
- Progressive respiratory failure if left untreated
- Disseminated TB with involvement of multiple organs
- TB meningitis - serious neurological complication with high mortality
- MDR-TB complications - treatment resistance and higher mortality rates
- Secondary bacterial infections and bronchiectasis
- Follow-up Tests
- If MTB DNA POSITIVE with Susceptibility (Drug-Sensitive TB):
- Chest X-ray - evaluate extent of pulmonary involvement and cavitary disease
- Culture and Drug Susceptibility Testing (DST) - confirmation and detailed resistance profile
- HIV testing - to assess TB-HIV co-infection status
- Liver Function Tests (LFTs) - baseline assessment before anti-TB therapy initiation
- Renal Function Tests - baseline assessment before anti-TB therapy
- Monthly sputum AFB smear microscopy - assess treatment response (negative at 2 months expected)
- Repeat TB-PCR at 2-3 months - assess molecular cure
- If MTB DNA POSITIVE with Rifampicin RESISTANT (MDR-TB):
- Extended Culture and DST - determine susceptibility to second-line drugs (fluoroquinolones, injectables)
- Line Probe Assay (LPA) or GenoType MTBDRplus - comprehensive resistance profile
- Baseline audiometry - before starting injectable agents
- Baseline vision testing - before fluoroquinolone therapy
- Electrolyte panel and renal function - for injectable drug monitoring
- ECG - baseline before bedaquiline therapy
- Monthly sputum AFB and TB-PCR - for treatment monitoring (longer duration required)
- If MTB DNA NEGATIVE:
- Repeat TB-PCR or culture if clinical suspicion remains high
- Investigate for alternative diagnoses (bacterial pneumonia, fungal infection, malignancy)
- Chest imaging if not already performed
- Ongoing Monitoring Frequency:
- Drug-Sensitive TB: Monthly sputum examination for first 3-4 months, then at end of treatment
- MDR-TB: More frequent monitoring - sputum AFB at each visit until conversion achieved
- Post-treatment follow-up: At 3, 6, 12 months after completion to detect relapse
- Fasting Required?
- NO - Fasting is NOT required
- Specimen Type:
- Early morning sputum (preferred) - first sputum sample after waking; has higher bacterial yield
- May also use: Bronchoalveolar lavage, cerebrospinal fluid, pleural fluid, lymph node biopsy, other body fluids
- Special Preparation Instructions:
- Sputum collection: Patient should rinse mouth with water (no mouthwash) before collection
- Cough deeply to produce sputum (minimum 2-3 ml recommended) - avoid contamination with saliva
- Collect in sterile container provided by laboratory
- Close container immediately and label with patient information
- Timing of Specimen Collection:
- Early morning sample is preferred - higher yield of TB bacilli
- Collect on any day of the week, any time is acceptable (though early morning preferred)
- Medications to Avoid:
- None - no medications need to be avoided specifically for specimen collection
- Note: If already on anti-TB treatment, specimen can still be collected and tested
- Transport and Storage:
- Transport to laboratory immediately or within 2-4 hours at room temperature
- If refrigerated, store at 2-8°C; may be stored up to 7 days with refrigeration
- Avoid freezing as it may reduce organism viability
- Additional Patient Information:
- Fasting is not required - patient can eat and drink normally
- No special diet restrictions before specimen collection
- Avoid using mouthwash or throat lozenges immediately before sputum collection
- Smoking status should be documented - may affect sample quality
How our test process works!
