Few facts about ppd test:
1. Receiving BCG vaccine MAY lead to positive test. As time goes by, it can turn back negative. So, if you received BCG as a kid (1year) and now at age 35 or so you are still positive, then you have peobably been exposed, and cant blame it on the vaccine
2. If you were negative for PPD in the past and now are positive then that should be taken as a serious sign of recent exposure.
3. If you are perfectly healthy, no cough, no wt loss, Normal chest X ray, and have a positive PPD, then you dont have TB, just exposure. In most of cases you dont need treatment. But if you are involved in taking care of kids (say child care center) or people with low immunity, then treatment is recommended so you dont transmit it to them. Even after treatment, the PPD will remain positive, as it indicates exposure and not infection.
4.Bigger the size of the "bump" more likely that you have been exposed.
5. Once PPD is positive, no point retesting in 1-2 years, it is probably still positive.
6. Make sure the nurse or doc is measuring it the right was, (vertical size along the length of the arm should not be measures, only the side to side, along the short axis of the arm should be measured) So if the lesion is 4 cm in length along the long axis of your arm and only0.9 cm along the short axis, then it should be read as negative.
