A 19-year-old G2P1 woman at 9 weeks' gestation presents to the obstetrics and gynaecology clinic for her second prenatal visit. She reports no complaints other than occasional nausea. She had her first child by spontaneous vaginal delivery without complications. She is taking no medications and denies ethanol, tobacco, or current drug use. While she does admit to a history of intravenous drug abuse, she denies using them since the birth of her first child. Over the past several months she has had multiple sexual partners and does not use contraception. On physical examination she is in no acute distress. Lungs are clear to auscultation bilaterally. Her heart has a regular rate and rhythm, with no murmurs, rubs, or gallops. She is informed that she will need the routine prenatal tests, including an HIV test. The physician informs her of the risks and benefits of the HIV test.1What else should the physician inform the patient before performing the test: