Tuberculosis Skin Test Reaction (Mantoux) Interpretation via Tuberculin (PPD) Reading
This test measures your reaction to a small amount of tuberculin protein injected under your skin to check for past or current exposure to tuberculosis (TB). It helps healthcare providers determine if you may have been exposed to *Mycobacterium tuberculosis* and assess risk for active TB infection.
["A simple skin test that helps identify possible TB exposure and guides further medical evaluation."]
Key facts at a glance
- LOINC
- 100764-0
- Short code
- M bovis reactn wheal 3D p Mam Tuberc Ql
- Synonyms
- M bovis reactn wheal 3D p Mam Tuberc Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
How the Test Works
A tiny amount of purified protein derivative (PPD) from tuberculosis bacteria is injected just under your skin on the inner forearm. After 48–72 hours, your healthcare provider checks the size of the raised, red bump (induration) or swelling at the injection site. This reaction indicates whether your immune system has ever encountered TB bacteria.
What to Expect During the Test
You’ll receive a small injection, and you may feel a slight pinch or mild discomfort. No special preparation is needed, but avoid scratching or picking at the injection site. The test is quick and painless, but you may experience mild redness or swelling at the site for a few days.
Interpreting Your Results
The size of your reaction (induration) is measured in millimeters. A positive reaction (typically ≥5 mm in most adults) suggests past exposure or latent TB infection. A negative reaction (no bump or <5 mm) usually means no recent exposure. Healthcare providers use these results alongside clinical judgment and other tests to guide further evaluation.
When This Test Might Be Ordered
Your doctor may recommend this test if you have risk factors for TB, such as living in or traveling to areas with higher TB rates, having an immune system weakened by conditions like HIV/AIDS, or being in close contact with someone with active TB.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is critical for identifying latent TB infection, which can develop into active TB if untreated. A positive reaction prompts further testing (such as a chest X-ray or TB blood tests) to assess risk and guide preventive treatment if needed. It helps prioritize care for those at higher risk of progression to active disease.
Short name
Tuberculin Skin Test (TST) Reaction Evaluation
Frequently asked questions
Why might my doctor ask for this test?
What does a positive test mean?
How long does it take to get results?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy