Off topic: tb test ambiguous

[Purplegirl2]

Any time I’ve had a tb skin test it has come back borderline. I’ve had to get the gold standard blood test and it’s come back negative. Wondering if my skin might be having a slight reaction to the preservative in the test, because I certainly am negative to tb. Just wondering how common it is or if anyone else has had this happen.

[deniseinmilden]

I don't know about people but false positives are a significant problem in cattle...

[fbirder]

cdc.gov/tb/publications/fac...

Some persons may react to the TST even though they are not infected with M. tuberculosis. The causes of these false-positive reactions may include, but are not limited to, the following:

Previous TB vaccination with the bacille Calmette-Guérin (BCG) vaccine

Infection with nontuberculosis mycobacteria (mycobacteria other than M. tuberculosis)

Incorrect measurement or interpretation of reaction

Incorrect antigen used

I tested positive as a little kid. The assumption was that I had a mild case of TB when younger.

[Purplegirl2 in reply to fbirder]

Thank you for your help!

[nellie237]

In the early 1970's when I was about 12 my mum caught TB. She knew exactly when she'd been infected because a woman behind her in a queue had coughed all over her....... we lived in London.

The whole family (I'm one of 6) had to be tested and we went to a small outbuilding in the hospital grounds (that wasn't in regular use ......and I know this because I lived in a house in the hospital grounds as dad was the senior engineer) where they'd set up an x-ray machine, and we all had chest x-rays. All were negative, and those of us that hadn't had it were given BCG's. Mum was allowed home earlier than was usual because she was 'within the hospital', but had to go and have IM injections every day in the hip area. The bruising from the jabs was horrendous, but she made a full recovery.

Roll on to the late 90's and my daughter's skin test indicated that she didn't need the vaccination. My daughter's best friend also had a grandmother who'd had TB, and she didn't need the vaccination either. I've assumed that my exposure to it passed protection onto my daughter.