interferon gamma release assay

Interferon-γ release assays (IGRA) are medical tests used in the diagnosis of some infectious diseases, especially tuberculosis. Interferon-γ (IFN-γ) release assays rely on the fact that T-lymphocytes will release IFN-γ when exposed to specific antigens. These tests are mostly developed for the field of tuberculosis diagnosis, but in theory, may be used in the diagnosis of other diseases that rely on cell-mediated immunity, e.g. cytomegalovirus and leishmaniasis and COVID-19.{{Cite journal |last1=Murugesan |first1=Kanagavel |last2=Jagannathan |first2=Prasanna |last3=Pham |first3=Tho D. |last4=Pandey |first4=Suchitra |last5=Bonilla |first5=Hector F. |last6=Jacobson |first6=Karen |last7=Parsonnet |first7=Julie |last8=Andrews |first8=Jason R. |last9=Weiskopf |first9=Daniela |last10=Sette |first10=Alessandro |last11=Pinsky |first11=Benjamin A. |last12=Singh |first12=Upinder |last13=Banaei |first13=Niaz |date=2021 |title=Interferon-γ Release Assay for Accurate Detection of Severe Acute Respiratory Syndrome Coronavirus 2 T-Cell Response |journal=Clinical Infectious Diseases|volume=73 |issue=9 |pages=e3130–e3132 |doi=10.1093/cid/ciaa1537 |pmc=7665338 |pmid=33035306}} For example, in patients with cutaneous adverse drug reactions, the challenge of peripheral blood lymphocytes with the drug causing the reaction produced a positive test result for half of the drugs tested.{{cite journal|title=Clinical implications of in vitro drug-induced interferon-gamma release from peripheral blood lymphocytes in cutaneous adverse drug reactions |journal=Journal of the American Academy of Dermatology |volume=52 |issue=2 |pages=254–261 | doi=10.1016/j.jaad.2004.05.006|pmid = 15692470|year=2005 |last1=Halevy |first1=S. |last2=Cohen |first2=A. |last3=Grossman |first3=N. }}

There are currently{{When|date=March 2025}} two IFN-γ release assays available for the diagnosis of tuberculosis:

• QuantiFERON-TB Gold (licensed in US, Europe and Japan); and{{Medical citation needed|date=March 2025}}
• T-SPOT.TB, a form of ELISpot, the variant of ELISA (licensed in Europe, US, Japan and China).{{cite web|url=http://www.tspot.com/about-the-test/t-spot-tb-test-works/|title= How the T-SPOT.TB Test Works}}{{Medical citation needed|date=March 2025}}

The former test quantitates the amount of IFN-γ produced in response to the ESAT-6 and CFP-10 antigens from Mycobacterium tuberculosis, which are distinguishable from those present in BCG and most other non-tuberculous mycobacteria. The latter test determines the total number of individual effector T cells expressing IFN-γ.{{citation needed|date=August 2022}}

The indications for the test are still disputed. It has been evaluated for the diagnosis of latent tuberculosis in HIV patients (who frequently have a negative Mantoux test).{{cite journal|title=Utility of interferon-γ ELISPOT assay responses in highly tuberculosis-exposed patients with advanced HIV infection in South Africa |vauthors=Lawn SD, Bangani N, Vogt M, etal |journal=BMC Infectious Diseases|year=2007|volume=7|pages=99|doi=10.1186/1471-2334-7-99|pmid=17725839|pmc=2031899 |doi-access=free }}