AFB-M.Tb Detection with Rifampicin resistance by CBNAAT BAL
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No Fasting Required
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PCR detection of TB with rifampicin resistance in BAL.
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AFB-M.Tb Detection with Rifampicin resistance by CBNAAT BAL
- Why is it done?
- Purpose: Detects acid-fast bacilli (AFB) and specifically Mycobacterium tuberculosis (M.Tb) in bronchoalveolar lavage (BAL) fluid samples, while simultaneously identifying rifampicin resistance
- Primary Indications: Suspected pulmonary tuberculosis with negative sputum smears; immunocompromised patients; suspected drug-resistant tuberculosis (MDR-TB)
- Clinical Settings: Patients with persistent respiratory symptoms despite negative sputum AFB; those with HIV/AIDS; patients with radiological findings suggestive of TB; follow-up evaluation of patients with prior TB treatment failure
- Technology Used: CBNAAT (Cartridge Based Nucleic Acid Amplification Test) - a rapid WHO-recommended molecular test providing results within 2 hours
- Normal Range
- Normal/Negative Result: Absence of MTB DNA detected; No rifampicin resistance detected
- Positive Result: MTB DNA detected; Reported as 'Positive' with or without rifampicin resistance
- Rifampicin Resistance Status: Reported as 'Resistant' or 'Susceptible'; Intermediate results occasionally reported
- Invalid/Inconclusive Result: May occur due to inadequate sample quality; requires repeat testing
- Units: Qualitative results (Positive/Negative); Resistance pattern (Resistant/Susceptible)
- Interpretation
- Negative Result (MTB Not Detected): No tuberculosis infection detected in BAL sample; However, does not completely rule out TB, especially in immunocompromised patients or with low bacterial load; Clinical correlation required
- Positive Result (MTB Detected) - Rifampicin Susceptible: Confirms active TB infection; Patient is susceptible to rifampicin; Standard first-line TB therapy can be initiated with rifampicin-based regimen
- Positive Result (MTB Detected) - Rifampicin Resistant: Confirms active TB with resistance to rifampicin; Indicates probable MDR-TB (Multi-Drug Resistant TB); Requires second-line anti-TB drugs; Urgent treatment modification and contact tracing necessary
- Specimen Quality Factors: BAL fluid volume and cell counts affect test sensitivity; Contamination or improper sample handling can lead to invalid results; Sample should contain adequate epithelial lining fluid
- Clinical Significance: Sensitivity approximately 95-98% for positive specimens; Specificity near 99%; Superior to smear microscopy; Particularly valuable in HIV-positive patients with lower bacterial loads
- Factors Affecting Results: Prior TB treatment; Previous anti-TB drug exposure; Bacterial burden in respiratory tract; Presence of non-tuberculous mycobacteria; Sample collection timing and technique
- Associated Organs
- Primary Organ System: Respiratory system (lungs, bronchi, bronchioles); Pulmonary alveoli where mycobacteria typically reside
- Conditions Associated with Abnormal Results: Active pulmonary tuberculosis; Multi-drug resistant TB (MDR-TB); Extensively drug-resistant TB (XDR-TB); Cavitary lung disease; Miliary tuberculosis; Tuberculous bronchitis
- Secondary Organ Involvement: Extrapulmonary TB affecting lymph nodes, pleura, liver, kidneys, central nervous system, and bones; Hematogenous dissemination in immunocompromised patients
- Potential Complications: Progressive lung destruction and fibrosis; Hemoptysis; Spontaneous pneumothorax; Respiratory failure; Development of cavitary disease; Treatment failure in rifampicin-resistant cases
- Associated Risk Factors: HIV/AIDS infection; Malnutrition; Diabetes mellitus; Chronic steroid use; End-stage renal disease; Immunosuppressive therapy; Malignancies
- Follow-up Tests
- If Result is Positive: Culture and drug susceptibility testing (DST) for isoniazid, ethambutol, and pyrazinamide; Liquid or solid TB culture from BAL or sputum samples; Full DST panel for second-line drugs if MDR-TB is confirmed
- Additional Diagnostic Tests: High-resolution CT chest; Sputum AFB smear microscopy (if sputum available); Chest X-ray for cavitary lesions; HIV testing (if status unknown); CD4 count if HIV-positive
- Monitoring During Treatment: Sputum AFB smear examination at 2 weeks, 2 months, 5 months, and end of treatment; Repeat CBNAAT BAL if clinical deterioration occurs; Monthly clinical assessment and symptom monitoring
- Complementary Tests: TB-LAMP (Loop-mediated Isothermal Amplification); GeneXpert MTB/RIF Xpert MTB/RIF Ultra for confirmation; Whole genome sequencing for resistance mutations
- If Result is Negative: Repeat BAL or sputum sampling if high clinical suspicion persists; Culture from BAL fluid; Consider other respiratory pathogens (fungi, atypical organisms); Repeat imaging if clinical condition warrants
- Post-Treatment Monitoring: End-of-treatment chest X-ray; Baseline sputum examination after treatment completion; Contact tracing and testing for household contacts; TB preventive therapy for contacts
- Fasting Required?
- Fasting: No - Fasting is NOT required for this test
- Pre-procedure Preparation: Normal diet and fluid intake permitted; Patient should be well-hydrated for procedure
- Bronchoscopy Preparation (for BAL collection): Typically requires 6-8 hours fasting from midnight if general anesthesia planned; Light meal and fluids allowed until 4-6 hours before procedure; Specific fasting guidelines per anesthesia team
- Medications to Avoid: Discontinue anticoagulants (warfarin, DOACs) typically 3-5 days before procedure; Hold antiplatelet agents (aspirin, clopidogrel) per protocol; Continue essential medications (cardiac, antihypertensive) with small sip of water if instructed
- Additional Instructions: Remove dentures, contact lenses, and jewelry before bronchoscopy; Void bladder before procedure; Wear comfortable, loose-fitting clothing; Arrange for responsible adult to accompany patient post-procedure; Avoid smoking for at least 24 hours before and after
- Sample Collection: BAL fluid collected during flexible fiberoptic bronchoscopy; Typically 20-60 mL of sterile normal saline instilled and aspirated; Sample placed in sterile container without preservatives; Transport to laboratory within 2 hours at room temperature
- Post-procedure Care: NPO (nothing by mouth) status until gag reflex returns (usually 1-2 hours); Avoid food and liquids initially; Monitor for adverse effects; Resume normal diet when appropriate; Rest for 24 hours; Report any chest pain, severe cough, or hemoptysis
How our test process works!
