What could this mean, if a few years ago I had a TB test, tested negative, and then just a few weeks ago, tested positive for TB. I know I am immunized against TB but I find it quite odd that I was tested positive when previously I had tested negative.
You don't specify which test was used to screen for TB, in this answer I will assume that Mantoux test was used.
You probably were vaccinated using Calmette-Guérin vaccine. Unfortunately this has been proven not to give an efficacious immunity against TB infection.
In this scenario there are two chances:
- You actually were exposed to M.Tuberculosis.
- The Mantoux test is probably a false positive due to your vaccination if you are at low risk for TB infection or to other factors.
Being at low risk means an individual was not:
- In contact with another person with infectious TB
- Born or has lived in a high TB prevalence country
- Continually exposed to populations where TB prevalence is high
In both cases I would personally advise you to contact a doctor to get a chest x-ray and a IGRA quantiferon blood test to further investigate. This is particularly advisable in your case having two different outcomes from serial testing which honestly could increase the possibility of latent TB.