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AFB-DNA (TB-PCR) Detection by RTPCR, Reflex to Rifampicin resistance by Ultra CBNAAT (Body Fluid)
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PCR + CBNAAT test to detect TB and rifampicin resistance in fluids.
₹2,146₹3,066
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AFB-DNA (TB-PCR) Detection by RTPCR Reflex to Rifampicin Resistance by Ultra CBNAAT (Body Fluid)
- Why is it done?
- Detection of Mycobacterium tuberculosis: Identifies TB infection through detection of AFB (Acid-Fast Bacilli) DNA in body fluids including cerebrospinal fluid (CSF), pleural fluid, pericardial fluid, and synovial fluid
- Rapid diagnosis of extrapulmonary TB: Enables quick detection of TB in non-respiratory sites such as meningitis, tuberculous pleurisy, and tuberculous arthritis
- Rifampicin resistance detection: Reflex testing with Ultra CBNAAT identifies mutations associated with rifampicin resistance, essential for detecting MDR-TB and initiating appropriate therapy
- Suspected TB meningitis: Patients presenting with meningeal symptoms and CSF abnormalities suspicious for tuberculous involvement
- Immunocompromised patients: HIV-positive individuals, patients on immunosuppressive therapy at higher risk for disseminated TB
- Suspected drug-resistant TB: Patients with TB risk factors, previous TB treatment history, or contacts of MDR-TB cases
- Normal Range
- Normal/Negative Result: NOT DETECTED or NEGATIVE - Indicates absence of Mycobacterium tuberculosis DNA in the body fluid sample
- Abnormal/Positive Result: DETECTED or POSITIVE - Indicates presence of M. tuberculosis DNA in the specimen
- Rifampicin Resistance Status (when test is positive): • RESISTANT - Indicates mutations in rpoB gene conferring rifampicin resistance • SUSCEPTIBLE - Indicates wild-type rpoB gene with rifampicin susceptibility • INDETERMINATE - Results unclear requiring further confirmation
- Units of Measurement: Qualitative (Presence/Absence of TB-DNA and resistance markers)
- Interpretation
- NEGATIVE Result: M. tuberculosis DNA not detected - TB unlikely in the tested body fluid. However, negative result does not completely exclude TB, especially with low bacterial burden or early infection. Clinical correlation and repeat sampling may be warranted if clinical suspicion remains high
- POSITIVE Result (TB-DNA Detected): Confirms presence of M. tuberculosis - TB diagnosis established with high specificity. Immediate initiation of anti-TB therapy recommended based on clinical presentation
- POSITIVE + RIFAMPICIN RESISTANT: Confirms TB with resistance to rifampicin - Likely MDR-TB. Requires initiation of second-line anti-TB drugs including fluoroquinolones and injectable agents. Urgent specialist consultation and drug sensitivity testing recommended
- POSITIVE + RIFAMPICIN SUSCEPTIBLE: Confirms TB with susceptibility to rifampicin - Drug-susceptible TB (DS-TB). Standard first-line anti-TB therapy (RIPE regimen) appropriate
- Factors Affecting Results: • Sample quality and adequate volume • Presence of PCR inhibitors in body fluid • Bacterial load in specimen (higher burden = more reliable detection) • Stage of disease (early vs established infection) • Prior anti-TB therapy • Proper sample collection and storage • Recent antibiotic exposure may affect sensitivity
- Clinical Significance: • Sensitivity: 75-95% for extrapulmonary TB (higher in TB meningitis) • Specificity: >99% - Positive result is highly specific for active TB • Superior to conventional AFB microscopy for body fluid specimens • More rapid than culture-based methods (results in 2 hours vs weeks for culture) • Allows simultaneous detection and drug resistance assessment • Particularly valuable in immunocompromised patients with low bacterial loads
- Associated Organs
- Primary Organ Systems Involved: • Central Nervous System (CNS) - TB meningitis affecting brain and spinal cord • Respiratory System - Pleural TB involving lungs and pleura • Pericardium - Tuberculous pericarditis affecting heart • Musculoskeletal System - TB arthritis affecting joints • Body cavities - Any serous membrane-lined space
- Common Diseases Diagnosed: • Tuberculous meningitis (TB meningitis) • Tuberculous pleurisy/pleural effusion • Tuberculous pericarditis • TB peritonitis • Tuberculous arthritis/osteomyelitis • Disseminated TB in immunocompromised hosts • Multidrug-resistant TB (MDR-TB)
- Potential Complications of Abnormal Results: • TB meningitis: Hydrocephalus, cranial nerve involvement, spinal cord compression, permanent neurological damage • Tuberculous pleurisy: Chronic empyema, lung fibrosis, respiratory compromise • TB pericarditis: Constrictive pericarditis, cardiac tamponade, heart failure • TB arthritis: Permanent joint destruction and disability • Disseminated TB: Multi-organ involvement, sepsis • MDR-TB: Limited treatment options, prolonged therapy, higher mortality rates • Drug-resistant strains: Treatment failure, development of extensively drug-resistant TB (XDR-TB)
- Follow-up Tests
- If Test is POSITIVE: • Chest X-ray or CT imaging - Assess pulmonary involvement and extent • Full drug susceptibility testing (DST) - Confirm rifampicin resistance status and test for other drug resistances (INH, fluoroquinolones, injectable drugs) • HIV testing - Determine immune status if not known • Sputum AFB smear and culture - If pulmonary TB suspected for infectivity assessment • Extended drug-resistant profile testing - For MDR-TB cases • Baseline liver and renal function tests - Before initiating anti-TB therapy
- If Test is NEGATIVE but Clinical Suspicion Remains High: • Repeat AFB-DNA PCR - Particularly if first sample had insufficient bacterial load • Conventional AFB microscopy and Ziehl-Neelsen staining - May detect organisms if not detected by PCR • M. tuberculosis culture - Gold standard diagnostic method (requires 2-8 weeks) • Imaging studies - CT brain for meningitis, chest CT for pleural disease • Adenosine deaminase (ADA) testing - On body fluid if TB meningitis suspected • Histopathology - If tissue biopsy obtained, granuloma assessment
- Monitoring During Treatment: • Clinical assessment - Monthly evaluation during treatment • Hepatic function tests - Monthly during intensive phase • Sputum microscopy conversion - At 2 months of therapy (if pulmonary TB) • Repeat imaging - To assess treatment response • Symptom assessment - For treatment-related adverse events
- Monitoring Frequency: • Weekly clinical assessment initially for severe disease (TB meningitis, TB pericarditis) • Bi-weekly during intensive phase of treatment • Monthly during continuation phase • Post-treatment follow-up at 3, 6, and 12 months after treatment completion • More frequent monitoring for drug-resistant TB and immunocompromised patients
- Complementary Tests: • Mantoux test/TST - Not useful for diagnosis but indicates TB infection • Interferon-gamma release assays (IGRA) - To differentiate latent TB from active disease • Complete blood count - Baseline and monitoring for treatment toxicity • Lymphocyte count - Particularly important in HIV-positive patients • Sputum TB-PCR - If concurrent pulmonary disease suspected
- Fasting Required?
- Fasting: NO - Fasting is not required for this test
- Sample Collection Requirements: • CSF (Cerebrospinal Fluid): 2-5 mL in sterile container for TB meningitis • Pleural fluid: 5-10 mL in sterile tube for pleural TB • Pericardial fluid: 5-10 mL in sterile tube for TB pericarditis • Synovial fluid: 2-5 mL for TB arthritis • Peritoneal fluid: 10-20 mL for TB peritonitis • All samples must be sterile and collected aseptically
- Special Instructions: • NO FASTING or dietary restrictions required • Patient may eat and drink normally before specimen collection • NO medications need to be withheld before the test • Specimens must be processed immediately (within 4 hours of collection) • If delay is unavoidable, refrigerate sample at 2-8°C but do not freeze • Maintain strict asepsis during sample collection (particularly important for body fluids) • Label specimen clearly with patient name, ID, collection site, and collection time
- Pre-Collection Preparation: • No specific patient preparation needed • Inform patient about procedure for specimen collection (lumbar puncture for CSF, thoracentesis for pleural fluid, etc.) • Obtain informed consent for invasive procedure • Explain that body fluid sampling procedure may have associated risks (infection, bleeding, organ damage) depending on collection site • Continue any ongoing medications unless specifically advised otherwise
How our test process works!
