AFB-Xpert panel by Combo(MTB /RIF Detection & AFB Culture)-Extrapulmonary Samples

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Combo test: TB DNA + rifampicin resistance + culture confirmation.

₹3,626₹5,180

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AFB-Xpert panel by Combo(MTB/RIF Detection & AFB Culture)-Extrapulmonary Samples

Why is it done?
- This test is performed to detect Mycobacterium tuberculosis (MTB) and rifampicin (RIF) resistance in extrapulmonary samples, combining rapid molecular detection (Xpert MTB/RIF) with acid-fast bacilli (AFB) culture capability
- Diagnosis of extrapulmonary tuberculosis including tuberculous meningitis, lymphadenitis, abdominal TB, pericarditis, peritonitis, and pleural TB from samples such as cerebrospinal fluid (CSF), lymph node biopsies, body fluids, and tissues
- Evaluation of patients with clinical and radiological signs suggestive of TB but with non-respiratory manifestations
- Assessment of suspected drug-resistant TB in extrapulmonary sites, particularly rifampicin-resistant tuberculosis (RR-TB) and multidrug-resistant TB (MDR-TB)
- Confirmation and speciation of mycobacterial cultures obtained from extrapulmonary specimens
- Typically performed when extrapulmonary TB is clinically suspected or confirmed, often urgently in cases of suspected tuberculous meningitis or disseminated disease
Normal Range
- Xpert MTB/RIF Result: Negative/Not Detected
- Rifampicin Resistance: Not Detected (indicates rifampicin susceptibility)
- AFB Culture: Negative/No growth
- Normal interpretation: Absence of MTB in the extrapulmonary sample indicates no tuberculosis infection at that site
- Units of measurement: Qualitative results (Positive/Negative); Ct values may be reported for Xpert MTB/RIF (lower Ct indicates higher bacterial load); Culture reports colony growth or no growth
- Normal vs Abnormal: Normal results (negative MTB detection, negative RIF resistance, no AFB growth) exclude TB in the sampled site; Abnormal results (MTB detected, RIF resistance detected, or AFB culture positive) indicate active TB infection and require immediate clinical intervention
Interpretation
- Xpert MTB/RIF Positive (MTB Detected): Confirms presence of MTB in the extrapulmonary site; indicates active TB disease; requires immediate anti-TB treatment initiation; Ct value helps gauge bacterial burden (very low Ct <15 indicates high bacillary load; high Ct >30 indicates low bacillary load)
- Xpert MTB/RIF Negative (MTB Not Detected): Does not exclude TB, especially in extrapulmonary samples which often have lower bacillary loads; consider repeat testing, alternative diagnostic methods (histopathology, imaging), or culture results; clinical correlation essential
- Rifampicin Resistance Detected: Indicates RR-TB or MDR-TB (rifampicin resistance is surrogate for MDR-TB in majority of cases); requires MDR-TB treatment regimen; necessitates further drug susceptibility testing for second-line drugs; significantly impacts treatment duration and outcomes
- Rifampicin Susceptible (Resistance Not Detected): Indicates susceptibility to rifampicin; suggests standard first-line TB therapy is appropriate; still requires full drug susceptibility testing before confirming susceptibility to other first-line agents
- AFB Culture Positive: Confirms MTB or other mycobacterial species; allows for speciation and comprehensive drug susceptibility testing; provides highest sensitivity for TB diagnosis; indicates viable organisms; time to positivity indicates bacterial burden
- AFB Culture Negative: May reflect low bacterial burden in extrapulmonary samples, dead organisms, inadequate sample, or absence of TB; does not exclude TB diagnosis, especially if Xpert is positive or clinical suspicion remains high
- Factors Affecting Results: Sample type and quality (paucibacillary extrapulmonary samples have lower sensitivity); sample volume; specimen processing and storage; prior anti-TB treatment (may reduce bacterial load); immunosuppression status; contamination
Associated Organs
- Primary Organ Systems Involved: Central nervous system (meninges in tuberculous meningitis); lymphatic system (lymph nodes); gastrointestinal tract (peritoneum, intestines); pericardium and heart; pleura and lungs (pleural involvement); bones and joints; genitourinary system
- Medical Conditions Associated with Abnormal Results: Tuberculous meningitis (CNS TB); TB lymphadenitis; abdominal TB (peritoneal, intestinal); TB pericarditis and constrictive pericarditis; pleural TB and effusions; TB arthritis; urogenital TB; cutaneous TB; TB adenitis
- Diseases Diagnosed or Monitored: Extrapulmonary tuberculosis; drug-resistant TB (MDR-TB and RR-TB); tuberculous meningitis; TB in immunocompromised patients (HIV/AIDS); disseminated TB; TB in children (often extrapulmonary)
- Potential Complications of Abnormal Results: Neurological sequelae in tuberculous meningitis (cranial nerve involvement, hydrocephalus, stroke); constrictive pericarditis from TB pericarditis; intestinal perforation in abdominal TB; chronic kidney disease in urogenital TB; spinal deformity from spinal TB; delayed diagnosis leading to dissemination; treatment failure from drug resistance
Follow-up Tests
- Recommended Based on Positive Results: Complete drug susceptibility testing (DST) for second-line anti-TB drugs if RIF resistance detected; full speciation and mycobacterial identification; HIV testing if status unknown; baseline liver and renal function tests before anti-TB therapy; chest X-ray or CT to exclude concurrent pulmonary TB
- Further Investigations if Negative Despite Clinical Suspicion: Repeat AFB culture and Xpert testing (paucibacillary disease may require multiple sampling); histopathological examination with Ziehl-Neelsen staining; TB-IGRA (Interferon-Gamma Release Assay) or tuberculin skin test; imaging studies (CT, MRI) appropriate to suspected site; clinical evaluation and consideration of empirical TB therapy if suspicion remains high
- Monitoring During Treatment: Repeat culture and susceptibility testing at 2-3 months to assess treatment response; clinical and radiological assessment at regular intervals; adherence monitoring; adverse effect surveillance; baseline and periodic hepatic and renal function tests; audiometry if using ototoxic drugs
- Complementary Tests Providing Additional Information: AFB smear microscopy (rapid but lower sensitivity); TB PCR for rapid confirmation; Adenosine deaminase (ADA) assay for TB pleuritis and meningitis; Chest X-ray for pulmonary involvement; CT/MRI for anatomical assessment of extrapulmonary disease; Histopathology with AFB staining for tissue diagnosis
Fasting Required?
- Fasting Required: No
- Fasting is not required for this test as it involves analysis of extrapulmonary clinical specimens (cerebrospinal fluid, tissue biopsies, body fluids) rather than blood samples
- Patient Preparation Requirements: No special dietary restrictions; patient may eat and drink normally; maintain normal medication schedule unless specifically instructed otherwise by the physician
- Sample Collection Preparation: Sample must be collected aseptically to prevent contamination; appropriate sterile containers must be used specific to sample type (sterile tubes for CSF, sterile containers for tissue, sterile tubes for body fluids); samples should be collected before antibiotic therapy if possible; samples should be transported immediately to the laboratory at appropriate temperature (room temperature for CSF and most body fluids, refrigerated for some samples)
- Medications to Avoid: No specific medications need to be avoided prior to specimen collection; however, if antibiotics or anti-TB drugs have already been started, this should be documented as it may affect culture results; timing of sample collection relative to antibiotic therapy should be noted
- Special Instructions: Adequate volume of specimen should be collected when possible; multiple samples may increase diagnostic yield, particularly for paucibacillary disease; clear labeling of specimen type and collection site is essential; inform laboratory if immunosuppression is present (HIV/AIDS) as it may influence interpretation; special handling protocols should be followed for biohazard materials

How our test process works!