Tuberculosis (TB) remains a significant public major health concern across India, but its effective control at individual level begins with awareness and proactive healthcare. Fortunately, early screening makes a world of difference, assisting your safeguard and your loved ones around you before symptoms arise.
One of the most widely used and reliable tools for screening tuberculosis (TB) is the Mantoux Test (also known as the tuberculin skin test). Used safely in clinical care for over a century, this quick skin test offers valuable insights into your immune system by detecting whether your body has ever encountered TB bacteria.
What is the Mantoux Test
The Mantoux Test, also called the tuberculin skin test, is a skin-based investigation used to detect exposure to the bacteria that cause tuberculosis. A small amount of purified protein derivative (PPD) is injected just under the skin intradermally. If the immune system has previously encountered TB bacteria through natural exposure or BCG vaccination, it mounts a localised response at the injection site within 48 to 72 hours.
The Mantoux Test does not diagnose active tuberculosis. It only reflects whether the body has been exposed to TB antigens at some point. Positive results need further investigation to distinguish between past exposure, latent infection and active disease.
How the Test is Performed
The procedure requires two visits and must be performed by some trained healthcare personnel. The following steps describe how the test is typically carried out.
- A trained healthcare worker cleans the inner forearm with an antiseptic swab.
- A small amount (0.1 mL) of purified protein derivative (PPD) solution is injected just beneath the top layer of the skin using a fine needle.
- A small, raised bump(wheal) appears at the injection site, indicating that the injection has been placed correctly.
- The patient is advised to keep the area clean and avoid scratching or covering it with tight dressings.
- The patient returns 48 to 72 hours later for assessment of the reaction.
- A trained reader measures the diameter of any raised, firm swelling (induration) across the forearm.
Mantoux test is interpreted based on induration, not redness. Only the firm swelling is clinically significant. The measurement is recorded in millimetres (mm) and documented for interpretation.
Reading the Result
The Mantoux test is interpreted by measuring the size of the induration (firm swelling) at the injection site 48 to 72 hours after administration. Interpretation also depends on an individual’s risk factors, medical history and likelihood of TB exposure.
Lupin Diagnostics follows standardised reading cut-offs applied in Indian clinical practice.
| Induration | Interpretation |
| Less than 5 mm | Negative |
| 5 mm or more | Positive in high-risk individuals |
| 10 mm or more | Positive in moderate-risk individuals |
| 15 mm or more | Positive in all individuals |
A qualified medical professional should interpret the result in the light of the patient’s clinical history, contact with TB patients, BCG vaccination status and immune condition.
Positive Vs Negative, Explained
A positive Mantoux test indicates that the immune system has recognised TB antigens and mounted a response to the tuberculin protein injected into the skin. However, it does not confirm active disease, nor does it specify whether the exposure was recent or long ago. Further additional clinical investigation such as a chest X-ray, sputum examination and sometimes an interferon-gamma release assay are usually requiring to clarify the picture.
A negative Mantoux Test suggests TB exposure is unlikely at the time of testing. However, a negative result does not completely rule out TB.False negatives can occur in very young children, malnourished patients, people with severe immune suppression and those with recent infection where the immune response has not yet developed.
Limitations And False Results
Although the Mantoux test is a valuable tool for tuberculosis screening, several factors can influence the accuracy of the result and should be considered during interpretation.
- BCG vaccination, common in India, may occasionally cause a positive reaction even in the absence of TB infection.
- Immune suppression such as that cause from HIV, chemotherapy or long-term steroids can produce false negatives.
- Non-tuberculous mycobacteria can sometimes produce cross-reactivity and contribute to a positive reaction.
- The test should be assessed 48 to 72 hours after administration, as readings taken earlier or later may not reflect the true response.
Mantoux test results should always be interpreted in conjunction with the patient’s symptoms, medical history, TB exposure risk, BCG vaccination status and overall immune health.
Choosing A Reliable Laboratory For Your Mantoux Test
Accurate Mantoux test results depend on proper administration, precise measurement of the skin reaction and consistent interpretation by trained healthcare professionals. Lupin Diagnostics offers Mantoux Testing and broader TB evaluation panels across India through its National Accreditation Board for Testing and Calibration Laboratories (NABL) accredited labs, with free home sample collection available in major cities.
The Bottom Line
The Mantoux Test remains one of the widely used screening tool for TB exposure, particularly in evaluating contacts of active cases and investigating suggestive symptoms. It is useful to note that proper administration, timely reading after 48-72 hours and interpretation within clinical context make the result far more significant. For a Mantoux Test or a complete TB workup, you can book a slot at lupindiagnostics.com or call 7030 300 400.
