Hi, and thanks for your question
When you have blood taken for an STI test, the blood sample gets sent to the laboratory for the actual testing. The lab tests the blood for whatever the nurse or doctor has ordered on the requisition (sheet of paper that gets sent with the blood). Some tests, like syphilis, HIV and Hepatitis A, B, & C can be run from the same sample of blood in the same tube. The only way to know what your blood is being tested for is to ask your testing provider which tests they are ordering on the requisition when they take your blood.
Let us know if this does not answer your question or if you have any more questions or concerns.