I would definitely talk to your doctor about this.  For that matter,
I'd think an equivocal test would probably be an indication for another
test.
    I received a BCG vaccine when I was 12, in 1965.  This was in Brooklyn,
NY.
    Years later I was required to get a ppd, and I told them not to
bother--I'd been told I would have a lifetime positive for TB.  They
insisted though (this was for my residency) and was surprised to get a
negative test.

Steve

This turns out to be a really complex question. You definitely want to
talk to your doctor about this. There won't be any way to be certain
whether the new positive PPD (TB test) is related to the old BCG
vaccination or infection with TB, although evidence of TB infection on a
chest x-ray would certainly be suggestive.

US recommendations, aimed mainly at protecting public health, would be
to ignore the prior BCG in deciding how to interpret and deal with the
positive PPD result, but those recommendations may or may not make sense
for an individual.

COMMENT:

Though BCG can cause a false positive in the PPD TB test, generally
the test is done anyway, unless the BCG is very recent (1 year), since
it usually takes a very recent BCG to give the clear false positive.
In your case, it's been so long it's almost certainly not going to
happen. The most severe reactions on the PPD (10 mm and certainly more
than 15 mm) are generally considered to be due to TB and never BCG.
The real interpretive problems are in people with BCG from a year or
so ago with intermediate reactions of 5 mm to 10 mm. Those are people
who in the past had to get X-rayed and re-tested, and sometimes even
treated with INH presumptively.

Fortunately, there's recently been approved now a nice blood test for
latent TB, which has controls for M. Avium and for BCG, so you can
answer this question for certain if you have a skin test in the
intermediate zone, and the question of BCG false positives becomes a
problem. It's called QuantiFERON. Check out.

http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5202a2.htm

I hope with the availability of the new blood test, we can at last now
start considering mass BGC vaccination in the US (which other than
Holland is the only Western country without a population vaccination
program for TB). Mostly it's the problem of false positives and
inertia which has held it up in the US. BCG is not a perfect vaccine,
and there's even some question if it prevents much pulmonary TB.
However, it does do some good, and the good is mounting as TB becomes
nastier. BCG does appear to decrease the multi-organ dissemination of
TB, and because it's an immune treatment, there's no doubt as
protective against dissemination from multi-drug resistant TB as any
other kind of TB. So if you ever get 5-drug or 6-drug resistant strain
of TB, you're gunna wish you had had it. That stuff spreading in your
bone marrow and lymph nodes might as well be AIDS. Or worse, because
we have a number of drugs that can slow down or hold most cases of
HIV.

I've had my BGC, which I obtained from Organon about 10 years ago and
did myself, somewhat clumsily (it works much better if you use an
insulin needle to poke yourself very shallowly through the vaccine
pool many times, rather than the silly magnet-and-tine-block set-up
you get from Organon, if that's what they still ship). I had to do my
own, because if you ask most US doctors about this, they won't know
what the devil you're talking about and will probably never have done
a TB vaccination. You can, however, get the TICE BCG even here in the
US, since it's approved for health care workers, but frowned upon and
not talked about, almost like it was a social stigma. My forearm had a
nasty sore for a month. But I have no scar now. Probably my immune
system will have some memory left if I should come across the real
bug. Just because your skin test goes back to "normal" doesn't
necessarily mean all your lymphocytes have forgotten everything. I'm
convinced that traces of immunity are left from every vaccine and
infection you ever had.

SBH