How can I know if I am free from sexually transmitted diseases?

Q: About 6 months ago I had oral sex with a girl following which I undertook the ELISA test which was negative. I have no problem (never experienced any burning sensation on passing urine or any infection on the penis) but have a doubt that if I go for VDRL (syphilis) test, the result may be positive. I have to go for a medical examination next week as I am flying to New Zealand and they will conduct the VDRL test. I am worried about the test. Shall I take the test before they conduct it? How can one know if he is free from any sexually transmitted disease? As I am not infected by HIV, will the VDRL be normal?

A:If the test for HIV was done more than 3 months after risk exposure, and thetest is negative then you are probably not infected with HIV. Only in rare cases the time taken for the test to become positive may be as long as 6weeks.If you had no symptoms and signs such as an ulcer or discharge, then you are unlikely to have a sexually transmitted infection (STI) though some people get infected and do not have obvious signs or symptoms. To be absolutely sure you can have a test done for syphilis and if positive get treatment before your medical. Please remember to avoid casual sex and exposure to risk of infection. If you cannot avoid casual sex, use a fresh condom from before sex to after withdrawing, even for oral sex.