Test false negative?

[jansky]

a few weeks ago i got tested for hiv, syphilis and chlamydia (possibly more) after an encounter with a sex worker a few months ago. the test results came back negative which is great; my question is could either of the following cause a false negative result:

- starting a course of doxycycline 2 days before the blood test?
- used the bathroom 30-45 minutes prior to the urine test?

also can chlamydia cause a rash on your body? what are the chances of contracting syphilis and not getting any primary stage symptoms like a chancre?

many thanks

[jansky]

i'm fairly sure it's unrelated to the doxy. it's probably nothing, but it's fairly easy to be sure. maybe i'll double check.

thanks

[auntiejessi]

I'm not saying it would cure it, but it could mask things enough to give you a false negative.  Its not likely, but its something that might be possible.

Did you get the rash after taking the doxy? Maybe its an allergic reaction to that.

Aj

[jansky]

i asked the doctor (about the doxycycline) when i got the test, he didn't seem to think it would affect the test or at least didn't seem very interested.

from what i understand, treatment for syphilis months after exposure (around 7. assuming this would make it secondary stage) would required about 3 weeks of oral doxycycline. i'm thinking 2 days wouldn't be enough to fight it out of the blood stream?

from what i can tell, the rash isn't typical or similar to those described as syphilis symptoms. it's certainly not on the hands, feet or genitals. the doctor also had a look at it and didn't think it looked related.

i'm only really asking for out of concern for my partner (who knows about the situation). i could just be paranoid anytime i see something small now, but thought it might be worth getting an opinion from a doc on the forum or something.

thanks again

[auntiejessi]

Oh the doxy would only affect a syphilis test, and that's only a maybe.  Your HIV test is fine.

Aj

[auntiejessi]

The doxy might affect a blood test, and syphilis can cause a rash.  You might have had a chancre and not noticed it.

Using the bathroom that soon prior to testing might affect it, but if you took doxy 2 days prior to that, the doxy could also affect a urine test.

I would wait until 2 weeks after finishing the doxy to test again for everything, and this time, wait at least an hour before giving a urine sample.

Aj