What is the recommended screening test for Human Immunodeficiency Virus (HIV)?

Recommended Screening Test for HIV

The standard recommended screening test for HIV infection is a combination HIV antibody/p24 antigen test (4th generation assay), followed by confirmatory testing with HIV-1/HIV-2 antibody differentiation immunoassay if reactive. 1

Initial Screening Test

The recommended screening approach follows a specific algorithm:

1. Combination HIV antibody/p24 antigen test (4th generation assay)

   • Sensitivity and specificity >99.5%
   • Detects both HIV antibodies and p24 antigen
   • Allows earlier detection of HIV infection than antibody-only tests

2. If initial test is reactive:

   • Proceed to HIV-1/HIV-2 antibody differentiation immunoassay to confirm and differentiate between HIV-1 and HIV-2 antibodies

3. If differentiation assay is negative:

   • Perform qualitative or quantitative Nucleic Acid Amplification Test (NAAT) to rule out acute HIV-1 infection 1

Testing Methodology

• Traditional approach: Enzyme-linked immunosorbent assay (ELISA) confirmed by Western blot or indirect immunofluorescence assay (IFA)

  • Highly accurate with sensitivity and specificity ≥99% 2
  • Detects antibodies to HIV

• Rapid HIV antibody testing:

  • Can be performed in 10-30 minutes
  • Useful for screening high-risk patients who don't receive regular medical care
  • Particularly valuable in emergency departments and for women with unknown HIV status in active labor 2
  • Several FDA-approved options available for use with whole blood, plasma, serum, or oral fluid specimens 2

Special Considerations

Pregnant Women

• All pregnant women should be tested during each pregnancy
• "Opt-out" screening strategies (where testing is performed unless explicitly declined) have shown higher testing rates
• Early identification allows antiretroviral treatment to prevent mother-to-child transmission 2, 1

Infants and Children

• For infants under 18 months, HIV DNA PCR testing is preferred over antibody testing due to the presence of maternal antibodies
• Testing schedule for HIV-exposed infants: before 48 hours of age, at 14 days (if available), at 1-2 months, and at 3-6 months 1

High-Risk Populations

• More frequent screening (every 3-12 months) is recommended for high-risk individuals
• High-risk settings include STD clinics, correctional facilities, homeless shelters, tuberculosis clinics, clinics serving men who have sex with men, and adolescent health clinics with high STD prevalence 2, 1

Common Pitfalls

1. False negatives during window period:

   • Antibody tests cannot rule out infection that occurred less than 6 months before the test
   • HIV antibody is detectable in ≥95% of patients within 6 months of infection 2

2. False positives with rapid tests:

   • Some authorities recommend confirming a positive oral rapid test result with a whole blood rapid test due to potentially higher false-positive rates with oral testing 2

3. Relying solely on risk assessment:

   • Risk factor assessment can miss 20-26% of HIV-positive clients who report no risk factors 2

4. Inadequate confirmatory testing:

   • Reactive screening tests must be confirmed by Western blot or indirect immunofluorescence assay
   • For definitive diagnosis in infants, two positive virologic tests on separate blood samples are required 2, 1

Screening Recommendations

• All sexually active individuals should be screened at least once in their lifetime
• Persons at increased risk should be screened more frequently
• Targeted screening efforts should be implemented in high-prevalence settings (defined as ≥1% prevalence) 2, 1

After confirming HIV infection, additional testing should include HIV genotype to assess resistance, CD4 cell count to assess immune status, and HIV viral load to establish baseline viral activity 1.