The CDC and other medical organizations prefer interferon-gamma release assays (IGRAs) for certain patient populations—here’s why you should, too

IGRAs offer many advantages over the tuberculin skin test

With a single visit and a highly accurate, objective result unaffected by the BCG* vaccine, IGRAs are the preferred method for many patient types compared to the century-old Mantoux tuberculin skin test (TST). When you’re ready to make the switch, only Quest Diagnostics offers a choice of tuberculosis (TB) blood tests: T-SPOT®.TB and QuantiFERON®- TB Gold Plus (QFT-Plus), both of which have a single-tube collection option.

*Bacille Calmette-Guérin

TST: subjective reading/interpretation Mantoux tuberculin skin test
  • Two patient visits required1
  • Manual results entry
  • Sensitivity 95%–98% in patients with proven active tuberculosis,2 specificity as low as 59% in BCG-vaccinated patients (high false positives)3

*The photograph was originally published in the Valley Echo and has been reproduced with the permission of the Lung Association of Saskatchewan.

TB blood tests: objective resulting T-SPOT®.TB and QFT-Plus

The new: TB blood tests
T-SPOT®.TB and QuantiFERON®-TB Gold Plus

  • Results available from a single patient visit1
  • Option for electronic results (reported straight to EMR)
  • T-SPOT.TB – estimated sensitivity: 95.6%†,4; estimated specificity: 97.1%††,4
  • QFT-Plus – estimated sensitivity: 94.09%†††,5; estimated specificity: 97.27%††††,5
  • Flexible collection options: 1-tube or 4-tubes
Groups with poor rates of return for TST reading1
Individuals who have received BCG vaccination1 
USCIS immigration exams6
Quest Diagnostics is committed to providing the most advanced TB screening available, in accordance with clinical guidelines.

Tuberculosis screening guidelines have been updated to include modern TB infection testing methods, including interferon-gamma release assays or TB blood tests, to address the limitations of the tuberculin skin tests.

The United States Preventive Services Task Force7

Grade B recommendation:

  • Screening for latent TB infection (LTBI) in populations at increased risk
    • Foreign-born adults from higher prevalence countries, regardless of age, duration in the US, or co-morbidities
    • Individuals in congregate settings
  • Ensures LTBI screening for at-risk adults is covered by most private health plans, Medicaid, and Medicare
American Thoracic Society, Infectious Diseases Society of America, and CDC2
  • IGRAs are preferred for patients >5 years of age with low to intermediate risk of progression, regardless of BCG status or likelihood of returning2
  • IGRA or TST can be used without preference in individuals >5 years of age with high risk of progression2
  • TST is preferred for children <5 years of age, but IGRA is acceptable2
  • American Academy of Family Physicians (AAFP) endorses these guidelines8
American Academy of Pediatrics9
  • Interferon-gamma release assays or tuberculin skin test can be used to detect TB infection among at-risk children >2 years of age
  • IGRAs are preferred for children who are BCG-vaccinated or unlikely to return
  • Children with HIV infection should receive annual IGRA testing or TST
  • Risk assessment for TB should be performed at the first encounter and then annually
American College of Rheumatology10
  • TB screening in all rheumatoid arthritis (RA) patients being considered for therapy with biological agents, regardless of the presence of risk factors for TB infection
  • IGRA is preferred if patient has a history of BCG-vaccination
  • IGRA can be performed as an initial test in all RA patients, in annual testing, and where TB exposure is likely
  • In immunosuppressed RA patients with risk of TB exposure, a repeat test can be considered 1–3 weeks after initial negative result
  • Annual TB screening in RA patients who live, travel, or work in environments where TB exposure is likely while continuing treatment with biologics

Your Quest representative can help you decide which TB blood test may best serve your practice. Either option includes additional advantages from Quest, including broad health plan coverage, access to a single-tube draw option, and easy test ordering and tracking through our Quanum™ Lab Services Manager.

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

a The CPT codes provided are based on AMA 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.
Learn more about QuantiFERON-TB Gold Plus  
Learn more about T-SPOT.TB

Questions? Call 1.866.MYQUEST (1.866.697.8378)

Image content features models and is intended for illustrative purposes only.

†The sensitivity of the T-SPOT®.TB test was estimated from subjects where it was known that active, culture confirmed TB infection was present.4

††The specificity of the T-SPOT®.TB test was estimated from subjects that were presumed as much as possible to have a lower probability of TB infection. “Low risk” subjects were selected on the basis of the absence of clinical, epidemiological and diagnostic risk factors for TB infection. 4

†††While there is no definitive standard test for LTBI, a suitable surrogate is microbiological culture of M. tuberculosis because infection with TB is a necessary precursor to disease.5

††††A multi-center study evaluating the clinical specificity of the QFT-Plus was performed on subjects who were considered to have either low risk of M. tuberculosis infection or no risk factors for exposure to infection or disease.5

T-SPOT®.TB and QFT-Plus are approved by the US FDA.
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-y) 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 product-specific warnings and other information can be found at www.tspot.com.

QFT-Plus is approved by the FDA as an in vitro diagnostic aid for detection of Mycobacterium tuberculosis infection. It uses a peptide cocktail simulating ESAT-6 and CFP-10 proteins to stimulate cells in heparinized whole blood. Detection of IFN-y by ELISA is used to identify in vitro responses to these peptide antigens that are associated with M. 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. Up-to-date licensing information and product-specific disclaimers can be found at www.QuantiFERON.com.

References

  1. Centers for Disease Control and Prevention. Latent tuberculosis infection: a guide for primary health care providers. https://www.cdc.gov/tb/publications/ltbi/diagnosis.htm#twoStepTSTTesting. Last reviewed October 20, 2014. Accessed April 12, 2019.
  2. Lewinsohn DM, Leonard MK, LoBue PA, et al. Official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention clinical practice guidelines: diagnosis of tuberculosis in adults and children. Clin Infect Dis. 2017;64(2):e1-e33. https://www.thoracic.org/statements/resources/tb-opi/diagnosis-of-tuberculosis-in-adults-and-children.PDF. doi:10.1093/cid/ciw694.
  3. Pai M, Zwerling A, Menzies D. (2008) Systematic review: T-cell-based assays for the diagnosis of latent tuberculosis infection: an update. Ann Intern Med. 2008;149(3):177–184.
  4. Oxford Immunotec. T-SPOT®.TB Package Insert PI-TB-US-V6. Abingdon, UK. May 2017.
  5. QuantiFERON-TB Gold Plus (QFT-Plus) ELISA Package Insert. 1095849 Rev. 04. July 2018.
  6. Centers for Disease Control and Prevention. Tuberculosis technical instructions for civil surgeons. Last reviewed September 5, 2018. https://www.cdc.gov/immigrantrefugeehealth/exams/ti/civil/tuberculosis-civiltechnical- instructions.html. Accessed April 12, 2019
  7. Bibbins-Domingo K, Grossman DC, Curry SJ, et al. Screening for latent tuberculosis infection in adults: US Preventive Services Task Force recommendation statement. JAMA. 2016;316(9):962–969.
  8. Tuberculosis: Guidelines for Diagnosis from the ATS, IDSA, and CDC. Am Fam Physician. 2018;97(1):56–58.
  9. Kimberlin DW, Brady MT, Jackson MA, Long SS. Red Book® 2018–2021: report of the Committee on Infectious Diseases. American Academy of Pediatrics. 2018.
  10. Singh JA, Furst DE, Bharat A, et al. 2012 Update of the 2008 American College of Rheumatology recommendations for the use of disease-modifying antirheumatic drugs and biologic agents in the treatment of rheumatoid arthritis. Arthritis Care Res. 2012;64(5):625–639.

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