Diagnostic Tests

What Physicians Need to Know

QuantiFERON-TB Gold+ for the Diagnosis of Mycobacterium tuberculosis Infection

 

Am Fam Physician. 2021 Feb 1;103(3):177-178.

QuantiFERON-TB Gold+ is a blood test used for the diagnosis of infection with Mycobacterium tuberculosis complex organisms (M. tuberculosis, M. bovis, M. africanum). It is used as an alternative to tuberculin skin testing for latent tuberculosis (TB). QuantiFERON-TB Gold+ is known as an interferon-gamma release assay (IGRA) because M. tuberculosis peptide antigens stimulate the release of interferon-gamma from the T cells of patients with the infection. It is the next generation of QuantiFERON IGRA testing. The previous generation is called QuantiFERON-TB Gold or QuantiFERON-TB Gold In-tube. Results of the blood test may be negative, positive, or indeterminate. A positive test result does not distinguish between active and latent TB.1 The U.S. Preventive Services Task Force recommends testing for latent TB in patients at increased risk of infection.2

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TestIndicationPopulationCost*

QuantiFERON-TB Gold+

Diagnosis of latent or active tuberculosis infection

Patients five years or older

$32 to $189


*—Range according to Quest Diagnostics, LabCorp, and San Francisco Department of Public Health.

TestIndicationPopulationCost*

QuantiFERON-TB Gold+

Diagnosis of latent or active tuberculosis infection

Patients five years or older

$32 to $189


*—Range according to Quest Diagnostics, LabCorp, and San Francisco Department of Public Health.

Accuracy

Cross reactivity is known to exist with three nontuberculous mycobacteria: M. kansasii, M. szulgai, and M. marinum. The proteins used to stimulate the cell-mediated response in patients are not found on any other nontuberculous mycobacteria or within the components of the bacille Calmette-Guérin (BCG) vaccine for TB. The manufacturer of QuantiFERON-TB Gold+ conducted seven sensitivity studies and four specificity studies across multiple sites in the United States, Japan, and Australia.1  Table 1 compares the specificity and sensitivity of tuberculin skin testing and the two major IGRA tests, QuantiFERON-TB Gold+ and T-SPOT.TB.1,35

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TABLE 1.

Sensitivity and Specificity of Tests for TB (Latent or Active) in Adults

TestSensitivity (%)Specificity (%)LR+LR−

QuantiFERON-TB Gold+

94.1

97.3

34.85

0.029

T-SPOT.TB

95.6

97.1

32.97

0.030

Tuberculin skin test

68.9

59

1.68

0.595


Reference standards used: QuantiFERON-TB Gold+ = culture or polymerase chain reaction of Mycobacterium tuberculosis (sensitivity), QuantiFERON-TB Gold (specificity); T-SPOT.TB = active TB diagnosis (sensitivity), control groups with extremely low TB risk (specificity); tuberculin skin testing = active TB diagnosis (sensitivity), control groups with extremely low TB risk (specificity).

LR+ = positive likelihood ratio; LR− = negative likelihood ratio; TB = tuberculosis.

Information from references 1 and 35.

TABLE 1.

Sensitivity and Specificity of Tests for TB (Latent or Active) in Adults

TestSensitivity (%)Specificity (%)LR+LR−

QuantiFERON-TB Gold+

94.1

97.3

34.85

0.029

T-SPOT.TB

95.6

97.1

32.97

0.030

Tuberculin skin test

68.9

59

1.68

0.595


Reference standards used: QuantiFERON-TB Gold+ = culture or polymerase chain reaction of Mycobacterium tuberculosis (sensitivity), QuantiFERON-TB Gold (specificity); T-SPOT.TB = active TB diagnosis (sensitivity), control groups with extremely low TB risk (specificity); tuberculin skin testing = active TB diagnosis (sensitivity), control groups with extremely low TB risk (specificity).

LR+ = positive likelihood ratio; LR− = negative likelihood ratio; TB = tuberculosis.

Information from references 1 and 35.

Benefit

QuantiFERON-TB Gold+ testing can be performed during a single visit and does not require a second interpretation visit, as with tuberculin skin testing. The results of QuantiFERON-TB Gold+ testing are objective, do not require training to interpret, and are not subject to variability in reading methods. QuantiFERON-TB Gold+ is more specific than tuberculin skin testing in patients with a history of BCG vaccination, and the BCG vaccine does not affect IGRA results.6

Harms

QuantiFERON-TB Gold+ testing and tuberculin skin testing are unable to distinguish between active and latent TB or predict the risk of progression from latent to active TB. IGRA testing requires a laboratory and is more difficult to perform in resource-limited environments.6 Although indeterminate results for IGRA tests

Address correspondence to Joseph R. Yancey, MD, at joseph.r.yancey.mil@mail.mil. Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

References

show all references

1. QuantiFERON-TB Gold Plus (QFT-Plus) [package insert]. Qiagen; 2018. Accessed May 20, 2020. https://www.quantiferon.com/us/wp-content/uploads/sites/13/2018/09/QFT-Plus-ELISA-IFU-L1095849-R04.pdf...

2. U.S. Preventive Services Task Force. Final recommendation statement. Latent tuberculosis infection: screening. September 6, 2016. Accessed July 28, 2020. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/latent-tuberculosis-infection-screening

3. Goletti D, Sanduzzi A, Delogu G. Performance of the tuberculin skin test and interferon-γ release assays: an update on the accuracy, cutoff stratification, and new potential immune-based approaches. J Rheumatol Suppl. 2014;91:24–31.

4. T-SPOT. TB [package insert]. Oxford Immunotec; 2017. Accessed August 2, 2020. http://www.oxfordimmunotec.com/international/wp-content/uploads/sites/3/Final-File-PI-TB-US-V6.pdf

5. Kabeer BSA, Raman B, Thomas A, et al. Role of QuantiFERON-TB gold, interferon gamma inducible protein-10 and tuberculin skin test in active tuberculosis diagnosis. PLoS One. 2010;5(2):e9051.

6. Haas MK, Belknap RW. Diagnostic tests for latent tuberculosis infection. Clin Chest Med. 2019;40(4):829–837.

7. 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):111–115.

8. San Francisco Department of Public Health. AITC Immunization and Travel Clinic. AITC regular prices. Accessed May 29, 2020. https://www.sfcdcp.org/aitc/aitc-regular-prices-low-cost-or-free-vaccines/

9. Quest Diagnostics. Secaucus, New Jersey. May 29, 2020.

10. LabCorp. Burlington, North Carolina. May 20, 2020.

11. Nijhawan AE, Iroh PA, Brown LS, et al. Cost analysis of tuberculin skin test and the QuantiFERON-TB Gold In-tube test for tuberculosis screening in a correctional setting in Dallas, Texas, USA. BMC Infect Dis. 2016; 16(1):564.

12. Mukai S, Shigemura K, Yamamichi F, et al. Comparison of cost-effectiveness between the quantiFERON-TB Gold-In-Tube and T-Spot tests for screening health-care workers for latent tuberculosis infection. Int J Mycobacteriol. 2017;6(1):83–86.

This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

A collection of Diagnostic Tests published in AFP is available at https://www.aafp.org/afp/diagnostic.

 

 

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