According to CDC guidelines an interferon gamma release assay may be used in place of (but not in addition to) a tuberculin skin test in all situations in which CDC recommends tuberculin skin test.
Interferon gamma release assays which measure the Th1-mediated immune response may pose a challenge even in clinical scenarios, such as pregnancy, in which Th1 immunity is altered. In cutaneous TB, this could be a problem as some of the cutaneous TB types show less immune response. So the sensitivity is unlikely to be more than Mantoux in Cutaneous TB. (My opinion)
|The Mantoux skin test consists of an intradermal injection of exactly one tenth of a milliliter (mL) of PPD tuberculin. (Photo credit: Wikipedia)|
I think, It will be helpful only to confirm MTB in a Mantoux Positive case with clinical suspicion. But only 1 visit is needed and the inter-observer interpretation variability is less.
I found out from the lab that it costs about US$ 230/-.
BTW, one of the first articles I read was about the use of IGRA in pregnancy. Their conclusion started like this:
Comparing the tuberculin skin test and interferon gamma release assay results in pregnancy.That would be a very risky comparison indeed! :-)