HIV Confirmatory Testing and Diagnosis

Confirmatory Testing Protocol

The Centers for Disease Control and Prevention recommends that all specimens reactive on initial HIV screening tests must be confirmed by Western blot or indirect immunofluorescence assay, even if subsequent conventional screening tests are not reactive 1, 2
Confirmatory testing is essential because screening tests alone are insufficient for diagnosis and may yield false-positive results 1
Some authorities recommend that a positive oral rapid test result be routinely confirmed with a whole blood rapid test due to potentially higher false-positive rates with oral testing 1

A confirmed positive result (positive Western blot or immunofluorescence assay) establishes the diagnosis of HIV infection 1
If confirmatory testing results are negative or indeterminate, follow-up testing should be performed on a blood specimen collected 4 weeks after the initial reactive HIV test 1

For pregnant women, the American Academy of Pediatrics recommends that preliminary positive HIV test results should receive antiretroviral prophylaxis while in labor with a recommended short-course regimen to prevent perinatal transmission prior to confirmation of results 1, 3, 4
For pregnant women, positive HIV antibody screening test results should be confirmed with immunofluorescent antibody or Western blot assay 3, 4
For high-risk individuals, the Centers for Disease Control and Prevention recommends additional serologic testing at 6, 12, and 24 weeks due to the window period 1
For high-incidence populations with recent exposure, an HIV RNA assay may be helpful in excluding acute HIV infection prior to starting preventive measures 5

The American Medical Association recommends ordering HIV RNA level (viral load) and CD4 cell count to characterize HIV stage 6
A general health assessment, including kidney and liver function tests, lipid levels, complete blood cell count, blood glucose level, and pregnancy test if applicable, should be performed 6
Screening for co-infections, including viral hepatitis A, hepatitis B, hepatitis C, tuberculosis, and sexually transmitted infections, is recommended 6
A baseline serum cryptococcal antigen test is recommended for individuals with CD4 cell counts below 100/μL, even without symptoms 6
Baseline reverse transcriptase-protease drug resistance genotype testing is recommended before initiating antiretroviral therapy 6

The American Medical Association recommends not delaying initiation of antiretroviral therapy while waiting for all laboratory results unless there is preexisting kidney or liver damage or high likelihood of transmitted drug resistance 6
The American College of Physicians recommends never initiating treatment for HIV until infection has been documented with confirmatory testing 7
Positive rapid HIV test results are preliminary and must be confirmed before establishing the diagnosis of HIV infection 8
Participants in HIV vaccine trials may have vaccine-induced antibodies that are detectable by HIV antibody tests and require specialized testing 8