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Reversing the rise in TB: IGRA blood tests screen for tuberculosis

Tuberculosis (TB) remains a leading cause of death in the United States by infectious disease, despite being both preventable and curable.1

Two distinct factors make now a critical moment for stronger tuberculosis precautions: the rising incidence of TB across the US,2 and the increased risk of TB complications in patients with diabetes, which is currently a major health concern nationwide. That’s why the US Preventive Services Task Force (USPSTF) recommends a rigorous screening protocol for latent TB infections in at-risk patients.3

By using preferred IGRA blood testing methods with the right patients sooner, healthcare providers can serve as an integral force in stemming the rising tide of TB prevalence.

In this article:

Clinical challenge | Why it matters | Ordering recommendations | Interpreting test results | Next steps | Supporting resources

 

Clinical challenge: Spike in TB cases paired with diabetes connection

Increase in active and latent tuberculosis infections

For the first time in more than 30 years, the incidence of active TB is once again increasing in the US. After an all-time low of 7,163 cases in 2020,4 more than 10,000 active TB cases were reported in 2024.5

The CDC cites several contributing factors for this uptick in TB:

  • Return to healthcare routines after pandemic-related disruptions
  • Increases in travel and migration after the pandemic
  • Localized outbreaks in multiple states

Inactive or latent tuberculosis infection (LTBI) cases are also climbing. It is estimated that approximately 13 million people carry LTBI,6 which is often asymptomatic—making it too easy to go unnoticed and undiagnosed. And that is a critical gap in care because about 80% of TB cases in the US stem from long-term, untreated LTBI.7

Connection to diabetes

The connection between diabetes and TB is strong. Patients with TB are 2 to 3 times more likely to have diabetes, and twice as likely to have poor outcomes—including death—during TB treatment.8

With nearly 15% of the US population diagnosed with diabetes,9 primary care providers are in a unique position to help prevent the progression of active TB in these patients by proactively screening for and treating TB infection.

The spike in TB cases, coupled with the connection to diabetes, makes it critical for providers to screen at-risk patients for this potentially deadly disease.

Why it matters: Multilayered risk factors for TB

While anyone can contract an active or latent tuberculosis infection, some populations are at significantly greater risk.2 Those with risk factors for TB include

Immigrants

Individuals born in, or former residents of, countries with high prevalence of TB

Immunocompromised

Patients with compromised immune systems are at significantly higher risk of progressing from latent infection to active TB2; this includes diabetes, HIV, many cancers (specifically hematologic, head and neck, and lung), and end-stage renal disease

Impacted by social factors

Social determinants of health, such as living/working or having lived/worked in congregate settings; these include homeless shelters, hospitals/health systems, and correctional facilities

Diabetes, HIV, cancer: Immunocompromised populations at greater risk of TB

23%+

of patients with TB also have diabetes10

 

 

9x

more likely for those with certain cancers to develop active TB11

4.9%

of patients with TB also have HIV12

Despite the alarming statistics, there is hope. TB, whether active or latent, is completely curable through treatment. By screening at-risk patients with recommended IGRA blood tests, providers have an opportunity to enable successful health outcomes and help reverse the trend of TB prevalence.

Latest guideline

The USPSTF recommends proactive IGRA blood test screening for asymptomatic adults over 18 who are at risk for TB.3

Ordering recommendations

Two broad types of testing are available to detect TB—blood tests or skin tests. However, the interferon-gamma release assay (IGRA) blood test is preferred for most at-risk groups by key health organizations, including the CDC, USPSTF, and WHO.3,13,14 Additionally, US Citizenship and Immigration Services requires IGRA TB testing for immigration exams.15

Recommended tests: QuantiFERON®-TB Gold Plus or T-SPOT®.TB IGRA blood tests

Quest Diagnostics is the only national commercial lab to offer a choice of TB IGRA blood tests.16

Both the QuantiFERON®-TB Gold Plus and T-SPOT®.TB tests are FDA approved, and samples can be drawn in a single visit with 1 tube. The QuantiFERON®-TB Gold Plus has the additional option of drawing 4 tubes.

 

QuantiFERON®-TB Gold Plus17
  • Sensitivity of 93.9% (n=398/423, CI 95%: 91.4%-96.0%)
  • Specificity of 97.3% (n=713/733, CI 95%: 95.8%-98.2%)
  • Objective results, available from a single patient visit
  • Flexible collection options: 1 tube or 4 tubes
  • Approved for patients who are immunocompromised and for children age 2+
  • 48-hour stability, refrigerated
  • Option for electronic results (reported straight to EHR)
  • Innovative CD4+ and CD8+ T-cell response delivers a more comprehensive evaluation of a patient’s immune response
  • Test codes: 36970 (1 tube), 36971 (4 tubes, draw site incubated)
  • CPT code: 86480
T-SPOT®.TBa,18
  • Sensitivity of 95.6% (n=175/183, CI 95%: 91.6%-98.1%)
  • Specificity of 97.1% (n=297/306, CI 95%: 94.5%-98.7%)
  • Objective results, available from a single patient visit
  • Easy specimen collection in 1 tube
  • Approved for patients who are immunocompromised and for children age 2+
  • Up to 54-hour stability, strict ambient
  • Option for electronic results (reported straight to EHR)
  • Exclusive to Quest
  • Test code: 37737
  • CPT code: 86481

 

Ordering details
QuantiFERON®-TB Gold Plus, 1 Tube
  • Test code: 36970
  • CPT code: 86480
 QuantiFERON®-TB Gold Plus, 4 Tubes, Draw Site Incubated
  • Test code: 36971
  • CPT code: 86480
 T-SPOT®.TB
  • Test code: 37737
  • CPT code: 86481

Note: The CPT codes provided are based on American Medical Association guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party.  Please direct any questions regarding coding to the payer being billed.

 

Why choose IGRA blood tests over skin tests

Modern, blood-based IGRA testing offers highly accurate, objective results significantly faster than the Mantoux tuberculin skin test (TST) that was developed more than 100 years ago.

IGRA blood tests are completed in 1 patient visit and results are straightforward, whereas TSTs require multiple visits and specialized experience to perform the test and read the results.

Who should receive an IGRA blood test

IGRAs are especially beneficial for those who have

  • A difficult time returning for a second test appointment
  • Compromised immune systems
  • Previously received the Bacille Calmette-Guérin (BCG) vaccine
  • Strong likelihood of being infected with TB
  • Low or intermediate risk of disease progression
  • US immigration exam requirements

 

Interpreting IGRA blood test results

IGRA TB blood tests measure immune response to TB proteins in whole blood.

QuantiFERON®-TB Gold Plus test results are reported as positive, negative, or indeterminate.

T-SPOT®.TB test results are reported as positive, negative, or borderline (equivocal).

The following conclusions can be found with either IGRA blood test:

  • Positive results mean the patient’s immune system has been exposed to TB bacteria, but the test cannot distinguish between latent and active TB; further clinical evaluation is needed to confirm or exclude active disease
  • Negative results suggest no TB infection, but false negatives may occur if the patient’s immune system is compromised (eg, by HIV, cancer, or certain medications)
  • Indeterminate or borderline results indicate the need for repeating the test with a new specimen

Find more details on results interpretation in the test FAQs:

 

Next steps: Rigorous treatment protocols and monitoring

Patients with positive results from their IGRA blood test need to be further evaluated to determine whether the infection is active or latent. This can include chest imaging and bacteriologic examinations of sputum specimens to diagnose or exclude active TB.

Whether active or latent, there are recommended treatment plans for TB infections that include strict regimens of medication on either a 4-, 6-, or 9-month timeline.19

Specialized medication options are available for the following unique cases:19

  • Drug-resistant TB infections
  • Children
  • Pregnant women
  • Patients with HIV

Due to the importance of not missing any doses or stopping treatment early, directly observed therapy (DOT) is often the best way to help patients fulfill the rigorous treatment plan requirements over the course of several months. DOT can be in-person or virtual.

Monitoring treatment effectiveness

Healthcare providers can monitor treatment progress and how the body is handling the medications by ordering blood, sputum, or urine tests. Patients being treated for active TB disease should also get additional chest x-rays.

 

Supporting resources

Tuberculosis testing web page
TB At-Risk brochure
TB Screening for Diabetic Patients sell sheet
TB Guidelines brochure (IGRA Guidelines)
TB Blood Testing vs Skin Testing brochure
QuantiFERON®-TB Gold Plus FAQs
T-SPOT®.TB FAQs

Clinical Education Center resources

Publication
Prevalence of Hepatitis B Virus and Latent Tuberculosis CoInfection in the United States
Pathology & Laboratory Medicine
Conference Presentation
Evaluating Testing Patterns and Prevalence Estimates of Hepatitis B Virus and Latent Tuberculosis Co-Infection from 2016 to 2020: A National Clinical Laboratory Database Analysis
Pathology & Laboratory Medicine
Conference Presentation
T SPOT TB Assay Using Extended Stored Blood Samples and Alternative Anticoagulant A Validation Study
View all articles

The T-SPOT®.TB test is an in vitro diagnostic test for the detection of effector T cells that respond to stimulation by Mycobacterium tuberculosis antigens ESAT-6 and CFP-10 by capturing interferon gamma (IFN-γ) in the vicinity of T cells in human whole blood collected in sodium citrate or sodium or lithium heparin. It is intended for use as an aid in the diagnosis of M tuberculosis infection. The T-SPOT®.TB test is an indirect test for M tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations.

Up-to-date relevant warnings, precautions, side effects, and contraindications can be found at http://www.oxfordimmunotec.com/north-america/

QuantiFERON®-TB Gold Plus (QFT-Plus) is an in vitro diagnostic test using a peptide cocktail simulating ESAT-6 and CFP-10 proteins to stimulate cells in heparinized whole blood. Detection of interferon-γ (IFN-γ) by enzyme-linked immunosorbent assay (ELISA) is used to identify in vitro responses to these peptide antigens that are associated with Mycobacterium tuberculosis infection.

QFT-Plus is an indirect test for M tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations.

 

 

References

 

  1. CDC. About tuberculosis. Published January 17, 2025. Accessed November 3, 2025. https://www.cdc.gov/tb/about/index.html
  2. CDC. Reported tuberculosis in the US, 2023. About the data. Published November 5, 2024. Accessed October 20, 2025. https://www.cdc.gov/tb-surveillance-report-2023/summary/index.html
  3. US Preventive Services Task Force. Screening for latent tuberculosis infection in adults: US Preventive Services Task Force Recommendation Statement. JAMA. 2023;329(17):1487-1494. doi:10.1001/jama.2023.4899
  4. CDC. Tuberculosis — United States, 2020. Published March 26, 2021. Accessed October 20, 2025. https://www.cdc.gov/mmwr/volumes/70/wr/mm7012a1.htm
  5. CDC. Provisional 2024 tuberculosis data, United States. Published March 15, 2025. Accessed October 20, 2025. https://www.cdc.gov/tb-data/2024-provisional/index.html
  6. CDC. Latent tuberculosis infection: a guide for primary health care providers. Published April 2024. Publication # 22-0468. Accessed October 20, 2025. https://www.cdc.gov/tb/media/pdfs/Latent-TB-Infection-A-Guide-for-Primary-Health-Care-Providers.pdf
  7. CDC. Latent TB infection in the United States – published estimates. Published October 18, 2024. Accessed October 20, 2025. https://www.cdc.gov/tb-data/latent-tb-infection-estimates/index.html
  8. van Crevel R, Critchley JA. The interaction of diabetes and tuberculosis: translating research to policy and practice. Trop Med Infect Dis. 2021;6(1):8. doi: 10.3390/tropicalmed6010008
  9. CDC. National Diabetes Statistics Report. Published May 15, 2024. Accessed October 20, 2025. https://www.cdc.gov/diabetes/php/data-research/index.html
  10. CDC. Reported tuberculosis in the US, 2023. Executive commentary. Published January 31, 2025. Accessed October 20, 2025. https://www.cdc.gov/tb-surveillance-report-2023/commentary/index.html
  11. Cheng MP, Abou Chakra CN, Yansouni CP, et al. Risk of active tuberculosis in patients with cancer: a systematic review and meta-analysis. Clin Infect Dis. 2017;64(5):635-644. doi:10.1093/cid/ciw838
  12. CDC. Risk factors. Updated January 31, 2025. Accessed October 20, 2025. https://www.cdc.gov/tb-surveillance-report-2023/summary/risk-factors.html
  13. Mazurek, GH, Jereb J, Vernon A, et al. Updated guidelines for using interferon gamma release assays to detect Mycobacterium tuberculosis infection—United States, 2010. MMWR Recomm Rep. 2010;59(RR-5):1–25. https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5905a1.htm
  14. WHO. Use of alternative interferon-gamma release assays for the diagnosis of TB infection - WHO Policy Statement. Published January 28, 2022. Accessed November 3, 2025. https://www.who.int/news/item/28-01-2022-use-of-alternative-interferon-gamma-release-assays-for-the-diagnosis-of-tb-infection---who-policy-statement
  15. CDC. Immigrant and refugee health. Tuberculosis. Published May 15, 2024. Accessed October 20, 2025. https://www.cdc.gov/immigrant-refugee-health/hcp/civil-surgeons/tuberculosis.html
  16. Data on file. Quest Diagnostics; 2024.
  17. QuantiFERON-TB Gold Plus (QFT-Plus) [package insert]. QuantiFERON; 2017.
  18. T-SPOT.TB [package insert]. Oxford Immunotec Inc; 2017.
  19. CDC. Treating tuberculosis. Published April 17, 2025. Accessed October 20, 2025. https://www.cdc.gov/tb/treatment/index.html

 

a Quest Diagnostics has validated the use of this assay under CLIA for processing specimens more than 8 hours after collection, up to 54 hours.

 

b Consult with your Quest Diagnostics sales representative for more details regarding stability in your area.

 

 

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