<s>[INST] Hello doctor,Three months ago, I was treated for syphilis with a shot of penicillin and other antibiotics. I was never tested for syphilis. I am a very active gay man who had signs of syphilis, and my infectious disease doctor presumptively treated me by providing antibiotics before I was tested. He told me to get tested as soon as possible, but I have never done. Two days after the antibiotics, my symptoms went away (I had swollen lymph nodes). I also experienced mild flu-like symptoms, which I understand, are common after syphilis treatment. So, I assumed it was syphilis and never got tested. Now I am worried that if I get reinfected, my doctor will not be able to tell. Should I be concerned? Currently under Biktarvy for HIV. Please help. [/INST] Hello. I understand that you are concerned. But serological tests for syphilis do not work like this. There are tests which remain positive for a lifetime if you once acquired syphilis. I dont know what features you had of syphilis but to confirm you have it or not you need to go for the serological tests, 1. TPHA (Treponema pallidum haemagglutination ) remains positive irrespective of the treatment taken for lifelong in most of the cases. So if it is positive, it will indicate the disease. 2. VDRL (venereal disease research laboratory) titers decrease after taking treatment, might become negative after treatment. Usually used to monitor the treatment response. Eg. If titer decreases, fourfold treatment is working fine. Not of much use if you did not have baseline VDRL in the first place. Still, get these two tests done and revert as there is no point in assuming that you had syphilis or not without these tests first. </s>