What is the next step after a patient receives positive initial screening results for Human Immunodeficiency Virus (HIV)?

Next Steps After Positive Initial HIV Screening Results

After a positive initial HIV screening test, a confirmatory test using Western blot or indirect immunofluorescence assay must be performed to establish the diagnosis of HIV infection. 1

Confirmatory Testing Protocol

• All specimens that are reactive on initial HIV screening tests (whether rapid tests or conventional ELISA) must be confirmed by Western blot or indirect immunofluorescence assay, even if subsequent conventional screening tests are not reactive 1
• 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

Interpretation of Results

• 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
• Indeterminate Western blot results may occur during early seroconversion and require additional testing to establish diagnosis 2

Special Considerations

For Pregnant Women

• Pregnant women with 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
• For pregnant women, positive HIV antibody screening test results should be confirmed with immunofluorescent antibody or Western blot assay 1

For High-Risk Individuals

• For persons with high-risk exposure within the past 3 months, additional serologic testing at 6,12, and 24 weeks may be necessary 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 1

Additional Laboratory Testing After Confirmed HIV Diagnosis

Once HIV infection is confirmed, the following tests should be ordered:

• HIV RNA level (viral load) and CD4 cell count to characterize HIV stage 1
• General health assessment: kidney and liver function tests, lipid levels, complete blood cell count, blood glucose level, and pregnancy test if applicable 1
• Screening for co-infections: viral hepatitis A, hepatitis B, hepatitis C, tuberculosis, and sexually transmitted infections 1
• Baseline serum cryptococcal antigen test for individuals with CD4 cell counts below 100/μL, even without symptoms 1
• Baseline reverse transcriptase-protease drug resistance genotype testing before initiating antiretroviral therapy 1

Clinical Pearls and Pitfalls

• Do not delay 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 1
• Never initiate treatment for HIV until infection has been documented with confirmatory testing 1
• Positive rapid HIV test results are preliminary and must be confirmed before establishing the diagnosis of HIV infection 1
• Repeat Western blot testing after initial diagnosis is generally unnecessary and wastes resources 3
• Participants in HIV vaccine trials may have vaccine-induced antibodies that are detectable by HIV antibody tests and require specialized testing 1

By following this structured approach to confirmatory testing after a positive initial HIV screening result, clinicians can establish accurate diagnoses and initiate appropriate care promptly, which is essential for improving patient outcomes.