The High St Medical Centre does a lot of "Gay Health" work, due to it's proximity to Commercial Rd Prahran.
If you are a guy, especially unmarried, they often encourage you to take a free set of STD tests and there is a Pathology lab on site. Guess it's because of the promiscuous community they operate in. I'd say if you were "well-dressed" they would insist on the STD checks.