STI Test: which blood markers matter?

For an STI (sexually transmitted infection) test, the relevant blood markers depend on the pathogen. For HIV, a combination test detecting p24 antigen and antibodies (HIV-1/2) is standard. Syphilis is diagnosed via TPHA/TPPA and RPR/VDRL in blood. Hepatitis B requires HBsAg, anti-HBc, and anti-HBs. For herpes simplex, IgG and IgM antibodies are measured, but IgM cannot reliably distinguish acute from past infection. Importantly, chlamydia and gonorrhea are typically not detected via blood but through urine or swab samples. Therefore, a blood-only test covers only a subset of STIs. False positives and negatives are possible, especially during the window period after exposure. Any positive result should be confirmed by a healthcare provider. MyBody-X does not currently offer specific STI blood markers; the markers listed are standard in clinical diagnostics. Evidence is based on medical practice, not randomized trials.