Assuming that the tuberculin test was performed with the standard Intermediate Strength preparation, a test result of 20 mm (of induration) is a strongly positive test and likely to be a true positive. While a large degree of induration does not correlate well with the degree of disease severity or extent, it is unlikely that an interferon (gamma) release assay would add anything more to the strong suspicion of active TB, on the basis of tuberculin testing.
To further assess your question, I would recommend that you and your physician refer to the 2010 recommendations of the Center for Disease Control (CDC) and/or consult with TB specialists at your local Public Health Dept. or with experts at the Institution National Jewish Health in Denver, Colorado.
Good luck
For more information, see the following abstract.
Is It Time to Replace the Tuberculin Skin Test With a Blood Test?
LoBue, Philip A. MD; Castro, Kenneth G. MD
JAMA: The Journal of the American Medical Association Issue: Volume 308(3), 18 July 2012, p 241–242
Dr. Tinkelman, Thanks for your answer.
I have read the article and I not really understand- if I receive a positive tuberculin test, there is very high chance that the t-spot answer will be too
positive?
Another Q- I understand that I need to take Antibiotics for Four months and I realized that the medicine have side effects, the side effect are stronger?
If I didint take the tretmaent, I have a 10% chance to get TB?
(Maybe I should take the risk?)
Thanks again for all your answers