Tuberculosis Skin Test Interpretation (Mantoux) – Induration Measurement (Serum/Plasma Substance Concentration)
This test measures the size of a raised area (induration) on your skin after a small amount of tuberculosis protein is injected. It helps determine if you may have been exposed to tuberculosis bacteria.
["A skin test result is not a blood test—it checks for immune response, not active infection."]
Key facts at a glance
- LOINC
- 82511-7
- Short code
- M bovis tuberc stim IFN-g Bld-aCnc
- Synonyms
- M bovis tuberc stim IFN-g Bld-aCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What This Test Does Not Measure
This compressed code refers to the **interpretation of a tuberculin skin test (TST)**, specifically tracking the size of the induration (hardened skin area) after injection. It does not measure tuberculosis bacteria in your blood or other body fluids. The actual TST involves injecting a small amount of purified protein derivative (PPD) under your skin, and a healthcare provider measures the induration 48–72 hours later.
How the Test Is Administered
You’ll receive an intradermal injection on your forearm or upper arm. The test site will be marked, and a healthcare provider will measure the size of the raised area (induration) and any redness (erythema) 48–72 hours later. The induration size is recorded in millimeters.
What to Expect After the Test
You may experience mild itching, redness, or swelling at the injection site. Avoid scratching or picking at the area. A red, raised bump could appear within 24–72 hours and may last a few days. Do not apply heat or ice to the site.
When This Test Is Ordered
This test is part of the **interpretation process** for a tuberculosis skin test (Mantoux test). It is typically ordered when evaluating risk for tuberculosis exposure, especially in high-risk groups (e.g., travelers, healthcare workers, or those with weakened immune systems).
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The induration size helps determine if your immune system has been exposed to tuberculosis bacteria. A positive result (typically ≥5 mm in high-risk individuals, ≥10 mm in others) suggests past exposure or infection. However, this test alone does not confirm active disease—additional testing (e.g., chest X-ray, sputum culture) may be needed for diagnosis.
Short name
TST Induration Reading (Serum-Based)
Frequently asked questions
Why is this test called a ‘serum-based’ measurement?
No. This test does not measure tuberculosis bacteria or antigens in your blood. It assesses your immune response to PPD protein via skin induration. For blood-based tuberculosis testing, you would need a different test (e.g., TB blood test or interferon-gamma release assay).
No. The TST requires a healthcare provider to administer the injection and measure the induration. It cannot be performed at home. Follow-up evaluation is always done in a clinical setting.
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