TB Medication

Hello,
I had a negative TB skin test in 2005 now I have a Positive skin test. The x-ray came back negative. I had the BCG vaccine when I was younger in the Caribbean. Had consultation recently physician told me I have to take Isioniazid medication. Is there any other test to check if I have TB. I have no symptoms showing TB. Could there be traces of the BCG vaccine in my body that causes the skin test to reflect positive. Also can this medication damage my Liver I am really worried about my health. Should I take the medication?
Thanks for your Advice

[National Jewish Health]

There are blood tests for tuberculosis (TB) that can be used to evaluate the significance of a positive tuberculin test.  The QuantiFERON-TB® Gold (QFT-G) test and the QFT-GIT test are examples of such tests; the latter reported to show enhanced sensitivity, while maintaining high specificity.

Your situation is complicated by the history of Bacille Calmette-Guerin (BCG) administration and an apparent skin test conversion from 2005 to 2008.  It is possible that the 2005 skin test was falsely negative and that the 2008 positive test is due to the BCG.  Ordinarily a documented skin test conversion is an indication for isoniazid (INH) prophylaxis.  Another consideration, in this regard is that not all TB is pulmonary and the positive 2008 test could be a reflection of TB elsewhere in the body.

You should seek a second opinion from a physician, quite experienced in the diagnosis and treatment of TB, including INH prophylaxis.  You might ask your doctor to recommend such a person or contact the local public health department for advice.

INH can be associated with liver toxicity, but the incidence of this adverse effect is low.  The risk of treatment must be compared with the risk of not treating, in a particular circumstance.  Once again, you should seek expert opinion.