Advantages
- A single visit to the lab blood draw site is required. (The IGRA test has been associated with higher levels of LTBI treatment completion and compliance.4)
- Results may be available within 24 hours.
- No booster phenomena are present.
- No errors like those associated with TST placement and reading.
- BCG vaccination does not usually cause a false positive as in TST. (This makes IGRA the preferred test for anyone who has received a BCG vaccine.)
Disadvantages
- QFT whole blood samples must be processed within 16 hours, while T-Spot blood cells must be processed within 8–32 hours. (This is because white blood cells must be fresh and viable.)
- Pre-examination errors in collection and transport, examination errors in running the test, or post-examination errors in interpreting the assay can be problematic.
- IGRAs are relatively new, and limited data exist on the use of IGRAs to predict the progression of TB disease.
- There is limited data on children under the age of 5 years, individuals recently exposed to M. tuberculosis, and immunocompromised.
- Limited data is available on serial testing.
4. Stockbridge, E., Loethen, A., Annan, E., & Miller, T. (2020) Interferon gamma release assay tests are associated with persistence and completion of latent tuberculosis infection treatment in the United States: Evidence from commercial insurance data. PLOS ONE, 15(12): e0243102. https://doi.org/10.1371/journal.pone.0243102
