MTB Susceptibility – Isoniazid Test: Booking, Price, and Results

The MTB Susceptibility – Isoniazid test checks whether Mycobacterium tuberculosis (MTB), the bacteria that causes tuberculosis (TB), is susceptible or resistant to isoniazid. Isoniazid is one of the most effective first-line drugs used to treat TB. Also known as the Isoniazid (INH) Susceptibility Test or INH Drug Susceptibility Testing (DST), this test is ordered for patients who have already been diagnosed with or are strongly suspected to have TB. A clinical specimen such as sputum or another relevant body fluid is collected and sent to the laboratory for analysis.

Doctors order the MTB Susceptibility – Isoniazid test to guide treatment decisions in patients with TB. Knowing whether the bacteria are resistant to isoniazid helps doctors choose the right drug regimen and avoid ineffective treatment.

Common Symptoms That May Require This Test

A doctor may recommend this test when a patient with confirmed or suspected TB presents with the following symptoms:

• Persistent cough lasting several weeks
• Fever and chills, often recurring
• Night sweats
• Unexplained weight loss
• Haemoptysis (coughing up blood)
• Ongoing fatigue and weakness
• Difficulty breathing or chest discomfort

Conditions This Test Can Help Detect

This test helps identify specific patterns of drug resistance in TB bacteria. The conditions it can help detect include:

• Mono-resistant TB (resistance to isoniazid alone)
• Poly-resistant TB (resistance to two or more TB drugs, but not both isoniazid and rifampicin together)
• Multidrug-resistant TB (MDR-TB), caused by bacteria resistant to at least both isoniazid and rifampicin
• Pre-MDR-TB, where isoniazid resistance may signal the early development of broader drug resistance

Preparation for the MTB Susceptibility – Isoniazid test is straightforward, but providing accurate clinical information is essential for correct result interpretation.

Do You Need to Fast?

No fasting is required for this test. You can eat and drink normally before sample collection.

Practical Tips Before Your Test

The following steps will help ensure a smooth and accurate sample collection:

• Bring a detailed clinical history, including your symptoms, previous TB test results, current medications and family history, as this information is required for the test.
• Provide your full address and mobile number at the time of registration, as these are needed for test coordination.
• If sputum is being collected, aim to collect an early-morning sample, which typically contains a higher bacterial count.
• Aim to collect at least 5 ml of sputum per sample.
• Inform your doctor about any ongoing anti-TB medications, as prior treatment can influence result interpretation.
• Wear comfortable clothing with easy access to the arm or collection site if a body fluid sample other than sputum is required.

Step-by-Step Procedure

The following steps describe the general process from sample collection to dispatch. If another sample type is collected (such as pleural fluid or CSF), the collection method will vary and will be performed by a healthcare professional at the collection centre.

1. Your doctor advises the most appropriate sample type based on your symptoms and suspected site of TB infection (sputum is the most common choice).
2. The sample is collected under proper biosafety conditions at the laboratory or healthcare facility.
3. At the lab, the specimen undergoes a decontamination process to remove other microorganisms while preserving the MTB bacteria.
4. The treated sample is placed into a growth medium and loaded into an automated culture system, such as the MGIT (Mycobacteria Growth Indicator Tube) system.
5. Once MTB growth is confirmed, small portions from the culture are transferred into tubes containing isoniazid at standard concentrations and observed for bacterial growth over a defined period.
6. The sample is stored and processed under refrigerated conditions, and results are reported after the observation period is complete.

Factors That Can Affect Accuracy

Several factors may influence the reliability of your test result:

• Quality and adequacy of the sample collected
• Bacterial load present in the specimen
• Prior or ongoing antibiotic or anti-TB treatment
• Mixed infection with different MTB strains, which can cause inconsistent results between testing methods
• Laboratory technique and adherence to standardised testing protocols

These general tips support effective TB management and help prevent drug resistance:

• Complete the full prescribed course of anti-TB treatment without interruption, even if you start feeling better.
• Never skip doses or stop medication without consulting your doctor, as incomplete treatment is a leading cause of drug resistance.
• Attend all follow-up appointments and repeat testing as recommended by your doctor.
• Maintain good nutrition and adequate rest to support your immune system during treatment.

MTB Susceptibility – Isoniazid test online booking is simple:

1. Select the test on the Lupin Diagnostics website.
2. Choose your city and preferred centre location.
3. Visit the centre at your scheduled time for sample collection.
4. Receive your report via email or WhatsApp within the stipulated turnaround time.