In 1981 I was exposed to TB. Just a postitive PPD test. I was on INH for a year. Knowing that once your a?

Question

positive your always a positive. Now.... If I am exposed to TB again how would I know it if all I am going to do is show positive? I am not concerned with xrays as they show only positive/active status. So I have to be active TB to find out that I was exposed again? Anyone know?

Answer 1

You're absolutely right... now that you have a positive PPD test, the PPD is of no value whatsoever in determining if you've been exposed.

Unfortunately, there isn't any other test that can be used instead of the PPD to determine if you've been exposed. Therefore, the strategy now changes to determining if you have active disease or not. If you're in a position where you're at high risk for contracting TB and passing it to others (the medical field is a classic example), they will screen you by your symptoms and possibly also by annual chest xrays. As you note, this will tell us only if you have active disease... it's the best that can be done at this point and if you think about it, whether or not you have active disease is the critical question. If you have active disease, you can spread it to others and you can die from it.

If all you have is a positive PPD or an exposure, well, you're not contagious and you won't die from it. You may develop the active disease later in life but if you're being screened regularly or develop symptoms, the doctors will be able to treat you at the time that the active disease crops up.

Incidentally, MOST people who have a positive PPD or an exposure DO NOT go on to develop active TB; just a small minority.