Mycobacterium tuberculosis (M. tuberculosis) QuantiFERON-TB Gold Plus (TB Blood Test) – Fluoroquinolone Resistance Mutation Screening
This blood test checks for specific genetic mutations linked to resistance to fluoroquinolone antibiotics in *Mycobacterium tuberculosis*, the bacteria causing tuberculosis (TB). It helps determine if TB treatment may need adjustments.
["This test assesses genetic mutations that could affect how well certain TB medications work."]
Key facts at a glance
- LOINC
- 72867-5
- Short code
- MTB gyrB fluoroquin res mut Islt/Spm Ql
- Synonyms
- MTB gyrB fluoroquin res mut Islt/Spm Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- molgen
- CPT
- 85610
- SNOMED
- 396252006
- 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
Why This Test Is Done
Your doctor may order this test if you have active or recent TB infection, especially if you’ve been treated with fluoroquinolones (like moxifloxacin or levofloxacin) or if resistance to these drugs is suspected. It helps guide treatment decisions to improve effectiveness and reduce risk of relapse.
What to Expect Before the Test
No special preparation is needed. A blood sample will be drawn from a vein, typically in your arm. The process takes about 5 minutes, and you may feel slight discomfort for a few seconds. You can eat and drink normally before the test.
What the Test Measures
The test detects mutations in the *gyrA* and *gyrB* genes of *M. tuberculosis*, which encode enzymes (DNA gyrase) that fluoroquinolones target. These mutations can make the bacteria less responsive to these antibiotics, requiring alternative treatments.
How the Results Are Used
Results help doctors tailor TB treatment plans. If mutations are found, they may recommend different antibiotics or longer treatment courses to ensure effective coverage. Negative results suggest fluoroquinolones are likely effective.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Fluoroquinolone-resistant TB is a growing concern, especially in regions with limited access to newer antibiotics. Identifying these mutations early can prevent treatment failures, reduce drug toxicity, and improve patient outcomes by avoiding unnecessary exposure to ineffective drugs.
Short name
TB Fluoroquinolone Resistance Mutation Test
Frequently asked questions
Will this test show if I already have TB?
How long will I need to wait for results?
Can I still take fluoroquinolones if this test is positive?
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