Genxpert

Lung

Report in 120Hrs

At Home

No Fasting Required

Details

Detects the DNA of Mycobacterium tuberculosis (MTB) and simultaneously identifies rifampicin resistance, a key marker for multidrug-resistant TB (MDR-TB)

₹3,900₹6,500

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Genxpert Test Information Guide

Why is it done?
- Rapid detection of Mycobacterium tuberculosis (TB) complex DNA in respiratory and non-respiratory specimens
- Simultaneous detection of rifampicin resistance, which indicates multidrug-resistant TB (MDR-TB)
- Diagnosis of active tuberculosis in patients with respiratory symptoms (cough >2 weeks, fever, night sweats, weight loss)
- Screening of HIV-positive patients with suspected TB infection
- Detection of TB in extrapulmonary specimens (pleural fluid, cerebrospinal fluid, lymph node tissue, urine)
- Contact tracing and confirmation of TB in exposed individuals
- Typically performed as first-line diagnostic test, with results available within 2 hours
Normal Range
- Test Result Interpretation:
- MTB Not Detected (Negative) - Normal/Negative result indicating no evidence of TB infection in the specimen
- MTB Detected; Rifampicin Resistance NOT Detected (Positive/Drug-Susceptible TB) - TB organism present; susceptible to standard first-line antituberculous drugs
- MTB Detected; Rifampicin Resistance Detected (Positive/MDR-TB) - TB organism present with resistance to rifampicin; requires second-line therapy
- Invalid Result - Error in test performance; specimen must be recollected and test repeated
- Units of Measurement:
- Qualitative reporting: Detected/Not Detected
- Semi-quantitative Ct (cycle threshold) values may be reported: High/Medium/Low TB load
Interpretation
- MTB Not Detected (Negative Result):
- Suggests absence of TB in the specimen tested; however, does not completely exclude TB in immunocompromised patients or those with low bacterial load
- Negative sputum Genxpert with high clinical suspicion may warrant repeat testing or additional diagnostic methods
- MTB Detected; Rifampicin Susceptible (Positive/Drug-Susceptible TB):
- Confirms active TB infection; patient is infectious and requires immediate isolation and initiation of first-line antituberculous therapy (isoniazid, rifampicin, pyrazinamide, ethambutol)
- Sensitivity: 98-99% for smear-positive TB; 95-98% for smear-negative TB
- MTB Detected; Rifampicin Resistant (Positive/MDR-TB):
- Indicates multidrug-resistant TB (resistance to both isoniazid and rifampicin); requires second-line therapy including fluoroquinolones and injectable agents
- Sensitivity for rifampicin resistance: 95-98%; Specificity: >99%
- Higher bacterial load (High Ct values) correlates with increased infectiousness and faster disease progression
- Factors Affecting Results:
- Quality and type of specimen (sputum samples superior to other specimens)
- Proper specimen collection and processing techniques
- Timing of specimen collection in disease course (higher positivity during initial infection)
- Immunological status (lower sensitivity in severely immunocompromised patients)
- Prior TB treatment or contamination with non-tuberculous mycobacteria
Associated Organs
- Primary Organ Systems:
- Respiratory system (lungs, bronchi, trachea) - primary site of TB infection
- Lymphatic system - involved in disseminated TB
- Central nervous system (CNS) - TB meningitis
- Skeletal system (spine, bones, joints) - tuberculous osteomyelitis and arthritis
- Genitourinary system - TB of kidneys and genital tract
- Conditions Associated with Abnormal Results:
- Pulmonary tuberculosis (PTB) - most common form
- Extrapulmonary tuberculosis (EPTB) - lymphadenitis, meningitis, pleuritis, pericarditis, peritonitis, osteomyelitis
- Multidrug-resistant tuberculosis (MDR-TB)
- Extensively drug-resistant TB (XDR-TB)
- Potential Complications Associated with TB (Abnormal Results):
- Massive hemoptysis and respiratory failure
- TB meningitis with neurological sequelae and death
- Spinal cord compression and paralysis (Pott's disease)
- Cardiac tamponade (TB pericarditis)
- Renal failure (TB nephritis)
- Treatment failure and drug resistance progression
Follow-up Tests
- If MTB Detected (Positive Result):
- Culture and drug susceptibility testing (DST) - gold standard for confirming TB and determining resistance patterns
- Line Probe Assay (LPA) or sequencing - for rapid detection of first-line and second-line drug resistance
- Chest X-ray - to assess extent of pulmonary TB
- HIV testing - to determine immunological status and guide TB treatment regimen
- Complete blood count (CBC) and liver function tests - baseline assessment before starting antituberculous therapy
- If MTB Not Detected (Negative Result) with High Clinical Suspicion:
- Repeat Genxpert with new specimen - false negatives can occur with low bacterial load
- Sputum microscopy (Ziehl-Neelsen or fluorescence staining) - complementary diagnostic method
- TB culture - reference standard with extended turnaround time (2-8 weeks)
- High-resolution CT chest - for detailed assessment of respiratory involvement
- Monitoring During Treatment:
- Repeat sputum smear microscopy at 2, 4, and 6 months of treatment to assess treatment response
- Monthly clinical review and adherence monitoring
- Baseline and periodic chest X-rays (at 2 months and end of treatment)
- Regular liver and renal function tests during antituberculous therapy
- Related Tests for Complementary Information:
- TB-LAMP (Loop-Mediated Isothermal Amplification) - alternative nucleic acid amplification test
- Interferon-Gamma Release Assay (IGRA) - detects TB infection but not active disease
- Tuberculin Skin Test (TST/Mantoux test) - screens for TB infection (limited specificity)
Fasting Required?
- Fasting Required: NO
- Genxpert is a respiratory specimen-based test and does not require fasting or dietary restrictions
- Specimen Collection Requirements:
- Early morning sputum (if available) - preferred due to higher mycobacterial yield
- Collect 2-5 mL of sputum in a sterile, labeled container
- Ensure specimen is deep, productive sputum - not saliva
- Specimen from other sites (cerebrospinal fluid, pleural fluid, lymph node tissue, urine) collected through appropriate clinical procedures
- Patient Preparation Instructions:
- Rinse mouth with water before sputum collection to minimize contamination with saliva
- Take deep breath and cough forcefully to produce specimen from lower respiratory tract
- No special medication restrictions; continue regular medications
- Avoid eating or drinking for 30 minutes before specimen collection if possible (improves specimen quality)
- Specimen Storage and Transport:
- Transport at room temperature within 48 hours of collection
- Use biohazard transport containers with proper labeling
- Avoid refrigeration of specimens (may reduce mycobacterial viability)

How our test process works!