GeneXpert MTB/RIF Test
About GeneXpert MTB/RIF Test
| Field | Value |
|---|---|
| Also Known As | Xpert MTB/RIF assay, CBNAAT (Cartridge-Based Nucleic Acid Amplification Test), TB GeneXpert, Xpert TB test |
| Sample Type | Sputum (expectorated or induced); cerebrospinal fluid, pleural fluid, tissue biopsy, and lymph node aspirate are also accepted |
| Fasting Required | No fasting required |
| Report Time | Results are typically available the same day or within 24 hours |
| Recommended For | Adults and children of all genders with suspected tuberculosis |
| Price | Starting at ₹2,400 |
What Is a GeneXpert MTB/RIF Test?
The GeneXpert MTB/RIF test is a molecular diagnostic test used to detect tuberculosis (TB) bacteria and to check whether they are resistant to a key TB medication called rifampicin. It is also known as the Xpert MTB/RIF assay or CBNAAT test. Doctors typically order it when a patient shows symptoms of active TB or when drug-resistant TB is suspected. The standard sample used is sputum, which is mucus coughed up from deep in the lungs.
What Does a GeneXpert MTB/RIF Test Measure?
The Xpert MTB/RIF assay uses real-time polymerase chain reaction (PCR) to analyse the sample at the molecular level. It looks for two specific things in the specimen.
| Parameter | What It Detects |
|---|---|
| Mycobacterium tuberculosis complex (MTBC) DNA | Genetic material from TB-causing bacteria, confirming whether TB bacteria are present in the sample |
| Rifampicin resistance (rpoB gene mutations) | Specific genetic changes in TB bacteria that indicate resistance to rifampicin, a first-line TB drug and a marker for multidrug-resistant TB (MDR-TB) |
Why Is a GeneXpert MTB/RIF Test Done?
A doctor may order a GeneXpert MTB/RIF test when there is clinical suspicion of tuberculosis or when a patient is at higher risk of drug-resistant disease.
Common Symptoms That May Require This Test
The following symptoms are among the common reasons a doctor may request this test:
- Persistent cough lasting longer than two weeks
- Coughing up blood or thick sputum
- Chest pain
- Unexplained weight loss or loss of appetite
- Persistent fatigue or weakness
- Fever and chills
- Night sweats
Conditions This Test Can Help Detect
This test can help identify the following conditions:
- Pulmonary tuberculosis (TB of the lungs)
- Extrapulmonary tuberculosis (TB affecting lymph nodes, spine, brain, pleura, or other organs)
- Multidrug-resistant tuberculosis (MDR-TB), identified through rifampicin resistance as a surrogate marker
- HIV-associated tuberculosis, where conventional tests may be less reliable
How to Prepare and What to Expect
No special preparation is needed for this test, but following a few steps will help ensure that the collected sample is of good quality.
Do You Need to Fast?
No, fasting is not required before this test. However, it is best to collect early-morning sputum before eating or drinking anything, as this sample tends to be richer in bacteria if an infection is present.
Practical Tips Before Your Test
Keep the following in mind before and during sample collection:
- Brush your teeth and rinse your mouth with plain water before collecting the sample. Do not use mouthwash.
- Collect sputum from deep in your lungs. It should be thick and sticky, not watery like saliva.
- If you struggle to produce sputum, breathing steam from a hot shower may help loosen secretions.
- Tell your doctor or the lab if you have already started anti-TB medication, as treatment lasting more than three days can affect the test's accuracy.
Step-by-Step Procedure
Here is what the sample collection process typically involves:
- You will be given a clean, sterile container for sputum collection.
- Take a slow, deep breath and hold it for about five seconds, then breathe out gently.
- Take another deep breath and cough firmly until sputum comes up into your mouth.
- Spit the sputum into the container. Aim for at least 5 ml (roughly one teaspoon).
- Close the container lid securely and write the date and time on the label.
- Hand the sample to the collection staff promptly. If delivery to the lab is delayed, the sample should be refrigerated.
Factors That Can Affect Accuracy
Several factors may influence how reliable the results are:
- Collecting saliva instead of true sputum from the lungs
- Delay in transporting the sample to the lab
- Improper storage (sample should be kept at 2°C to 8°C if not delivered immediately)
- Being on anti-TB treatment for more than three days before the test
- Very low bacterial load in the sample (paucibacillary disease)
Understanding Your GeneXpert MTB/RIF Test Results
Results from this test are qualitative, meaning they are reported as detected or not detected rather than as a number. A doctor will always review your results alongside your symptoms, medical history, and other test findings.
| Parameter | Expected Result | What It Means |
|---|---|---|
| MTB DNA Detection | Not Detected | No TB bacterial DNA found in the sample |
| Rifampicin Resistance | Not Detected | No resistance mutations identified in the rpoB gene |
These ranges are general guidelines. Your doctor will interpret your results based on your age, health history, and other factors. Always consult a qualified healthcare professional for personalised medical advice.
Results During Special Conditions
Certain circumstances can influence how the results should be read.
- HIV coinfection: Sensitivity of the Xpert MTB/RIF assay remains above 80% in HIV-positive individuals, though it may be slightly lower than in HIV-negative patients. The test remains a valuable diagnostic tool in this group.
- Prior TB treatment: The test detects DNA from both living and dead bacteria. Patients who have been on anti-TB therapy for more than three days may receive results that do not accurately reflect their current infection status.
- Low bacterial load: In samples with very few bacteria, such as smear-negative sputum or some extrapulmonary specimens, the test may be less sensitive. A culture test may be needed alongside or after the GeneXpert MTB/RIF test in such cases.
How to Maintain Healthy Levels
The following general steps can support respiratory health and reduce TB risk:
- If you have been in close contact with someone diagnosed with active TB, speak to a doctor about getting tested.
- Ensure good ventilation in your home and shared spaces to reduce the risk of airborne transmission.
- Seek medical advice early if you notice a persistent cough, unexplained weight loss, or night sweats.
Lupin Diagnostics GeneXpert MTB/RIF Test Price and Home Collection
The GeneXpert MTB/RIF test price at Lupin Diagnostics starts at approximately ₹2,400, with home sample collection available across major cities.
| City | Approximate Price (₹) |
|---|---|
| Mumbai | ₹2,400 |
| Bangalore | ₹2,400 |
| Chennai | ₹2,400 |
| Hyderabad | ₹2,400 |
| Kolkata | ₹2,600 |
| Pune | ₹2,400 |
Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
- Select the test on the Lupin Diagnostics website.
- Choose your city and preferred time slot.
- Opt for home sample collection by a certified phlebotomist, or visit your nearest Lupin Diagnostics centre.
- Receive your report via email or WhatsApp within the stipulated turnaround time.
Home Collection
Lupin Diagnostics offers home sputum sample collection across cities, making it easier to get tested without visiting a centre. All samples are processed in NABL-accredited laboratories by trained technologists. Digital reports are accessible via email or WhatsApp once ready.
Frequently Asked Questions
The GeneXpert MTB/RIF test results can be obtained in under two hours once the sample reaches the lab. Most patients receive their reports the same day or within 24 hours of sample collection.
Yes. The Xpert MTB/RIF assay is more sensitive than traditional smear microscopy, particularly when the bacterial load in the sample is low. Its negative predictive value is above 98%, meaning a negative result reliably rules out TB in most patients.
Yes. The test identifies mutations in the rpoB gene that indicate resistance to rifampicin. Since rifampicin resistance is closely linked to multidrug-resistant TB (MDR-TB), a positive resistance finding prompts further investigation.
A negative GeneXpert MTB/RIF test result makes TB very unlikely. However, if your doctor still strongly suspects TB based on your symptoms or other findings, additional tests such as a TB culture may be recommended.
Yes. While sputum is the most common sample, the Xpert MTB/RIF assay can also be performed on cerebrospinal fluid, lymph node aspirate, and tissue biopsies. It is particularly useful for diagnosing extrapulmonary TB when sputum is unavailable.
The test is designed for patients who have not yet started anti-TB treatment, or who have been on treatment for fewer than three days. If you have been taking TB medication longer than this, let your doctor know, as results may not be fully reliable.
GeneXpert MTB/RIF Test
