How common are false negative results from an HIV test?

How To Read HIV Test Results

• Answer:

  Human immunodeficiency virus (HIV) is transmitted through blood after contact with an infected person or contaminated needle, and it is the virus that causes acquired immunodeficiency syndrome (AIDS). When the virus enters your body, your immune system responds by producing antibodies against it. Laboratory testing for HIV antibody is generally the method doctors use to diagnose HIV. Difficulty: Moderately Easy Instructions Search your laboratory report for the test HIV antibody. Look for the terms "negative" or "undetected", "positive" or "detected." An undetected antibody (negative result) means that the disease is not present at the time of testing. A positive antibody result warrants further testing. Know that it takes the virus three to eight weeks after exposure to show in laboratory testing. Repeat testing three to six months after an initial screening is common among individuals at high risk of contracting HIV or those who believe they have been exposed. Realize that the laboratory confirms every positive screening for HIV antibody using a method called "Western blot," which tests for the presence of HIV proteins. A positive HIV screening and "Western blot" diagnose HIV infection. Tips & Warnings Tip: False positive (indicating the presence of the antibody when it is not there) can occur with initial HIV antibody screening. A positive screening for HIV antibody with a negative "Western blot" confirmation is considered a false positive. Screening is generally repeated three to six months later. Tip: HIV antibody screening detects the presence of antibody three to eight weeks after exposure to the virus. To test for HIV infection sooner, doctors may order a p24 antigen test that detects the viral protein one to three weeks after exposure, or HIV RNA test that tests for the presence of the virus itself. Tip: The Centers for Disease Control and Prevention (CDC) considers individuals with multiple sexual partners, those diagnosed with a sexually transmitted disease (STD) like syphilis, those who inject street drugs, individuals who received blood products transfusion between 1978 and 1985 and homosexual men to be among the high risk group for HIV infections and recommends frequent HIV antibody screening. Tip: An at-home collection kit for HIV allows you the privacy of getting tested at your home. You follow the instructions in the kit to collect a blood sample and mail the kit to the testing center. The testing center calls you with the result and appropriate counseling. Warning: Always consult your health care provider about your risk factors for HIV infection and ways to minimize exposure and transmission of the virus.