BCG test and Isoniazid prophylaxis treatment


Q: Hello, I just had a question. I recently had the TB (BCG) skin test and the results came out positive. Because the results are not always accurate, my doctor scheduled an appointment for me to have a chest x-ray completed. The chest x-ray came out negative. My doctor suggested that I go on isoniazid for 6 months stating that I might have latent Tb that I might have encountered when I used to live back home, stating that because my origin is in a third world country, that is where most people are infected with TB. I started the medication but I am feeling alot of discomfort in my liver and stomach. I consulted my doctor and was told this is normal. Now what comes to my mind is that how is it possible that I have TB when I received the immunization for it when I was 1 years old? By being vaccinated wouldn't my BCG test always come out positive anyway because my vaccine contained strains of tuberculosis bacillus? thank-you


A:   I understand your situation and would like to assure you that you don’t have TBC infection. However, there are some guidelines that have been established in order to decrease the incidence of TBC infected patients.
Certainly if you were vaccinated with the BCG, a response to the PPD test is expected. If you developed an induration of your skin of more than 10 cm in diameter they will send you for an X-ray just to see if there is an active infection. Since nothing showed, prescription with Isoniazid to clear the bacteria from your body is suggested but not because you have an infection, it is just given for you to decrease the chance of having an active infection.
In my opinion, Isoniazid treatment should be monitorized due its high risk of damaging the liver and I would also suggest you to take vitamin B6 since there is a mild depletion of this vitamin when taking that medication. I hope I cleared your doubt.

Related Q&A

Q: I'm suffering from pain in the lower abdomen and sometimes it goes all the way to my back and thigh but only on the l...

Q: Hi I had a medical termination almost 10 weeks ago and have still not had a period. The termination period wasn't th...

Q: Hello i had my last periods on 15 september i had unprotected sex with my boyfriend but he did not ejaculated in me,i...

Q: How do I get a circumcision when my GP says it's non threatening so I don't need one?

Q: Is it safe to masturbate while recovering from a concussion?


Dr. James Obaji M.D.

  • 247 Reviews
  • Family Physician

Dr. Suneel Sharman M.D.

  • 190 Reviews
  • Family Physician

Dr. Pat Golden M.D.

  • 169 Reviews
  • Cardiologist

Dr. Kunaal Jindal M.D.

  • 112 Reviews
  • Plastic Surgeon