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Mycobacterium tuberculosis-specific antibody, serum/plasma (immunoassay)

Published: August 9, 2026Updated: August 16, 2026

This blood test checks for antibodies to *Mycobacterium tuberculosis*, the bacteria responsible for tuberculosis (TB). Antibodies indicate if your immune system has ever been exposed to the bacteria, even if you never developed active TB.

Quick summary

["Helps determine past exposure to TB bacteria, not current infection status."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
105757-9
Short code
Mtb embC-embA ethambtl res mut Is
Synonyms
Mtb embC-embA ethambtl res mut Is
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
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

What This Test Measures

The test detects specific proteins (antibodies) produced by your immune system in response to *Mycobacterium tuberculosis*. These antibodies are created when your body encounters the bacteria, but they may remain in your blood for years after exposure. This test does not measure active TB infection or recent exposure.

Why It’s Ordered

Your healthcare provider may order this test if you have a history of TB exposure, live in an area with higher TB rates, or have symptoms like persistent cough, fever, or weight loss. It’s also used in screening for latent TB infection (LTBI) before certain treatments.

What to Expect

A small blood sample is drawn from a vein in your arm. The sample is sent to a lab where antibodies are measured using an immunoassay method. Results are typically available within 24–48 hours.

What the Results Mean

A positive result suggests past exposure to *Mycobacterium tuberculosis*, but it does not confirm active TB. A negative result means no detectable antibodies, indicating no past exposure or recent infection. Always consult your provider for interpretation, as results can vary based on timing of exposure and other factors.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

TB Antibody Test

Frequently asked questions

How long does it take to get results?
Results are usually available within 24 to 48 hours after the blood sample is processed, but timing may vary by lab. Your provider will contact you once results are ready.
Can a positive result mean I have active TB?
No. A positive TB antibody test indicates past exposure to the bacteria, not active infection. Active TB requires additional testing (e.g., chest X-ray, sputum culture) to confirm. Always discuss results with your healthcare provider.
Does this test replace a TB skin test?
No. While this test detects antibodies for past exposure, a TB skin test (TST) or interferon-gamma release assay (IGRA) is often used alongside it to assess active infection risk. Your provider may order both tests depending on your medical history and symptoms.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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