Table 2 below summarizes the most commonly used HIV detection methods, highlighting the advantages and disadvantages of each.
Table 2. HIV Detection Methods Comparison.| Method | Advantages | Disadvantages | Comments |
| Rapid anti-HIV-1/HIV-2 methods | - Ease of use
- Can be performed and interpreted while patients are still at the testing site; valuable for patient management, particularly in high prevalence areas and for high-risk individuals.
- Some methods allow alternate specimen types, such as oral fluids or urine.
- High sensitivity, if serum/plasma is used as the specimen type.
| - Will only be reactive if antibodies are present.
- Patient may be infectious, but the test will be negative if testing is performed during the window period (between infection and a detectable immune response).
- Method is less sensitive if an alternate specimen type is used due to less antibody present.
| A neonate should not be tested for HIV by using an anti-HIV method if the mother is seropositive. |
| HIV p24 antigen test | - Detects HIV infection before antibodies are produced (between 14 and 22 days post-infection).
| - Once antibodies begin to be produced, antigen diminishes below detectable levels.
| The greatest value is in antigen/antibody combination test methods. |
| Fourth and fifth generation antigen/antibody combination immunoassay methods (EIA or chemiluminescence) | - Increased sensitivity over previous test generations; can detect HIV IgM which is produced earlier in infection than IgG.
- Combines HIV p24 antigen detection with antibody detection.
| - False-positives are possible.
- Usually requires repeat testing if initially reactive and supplementary testing if repeatedly reactive.
| Fifth generation differentiates antigen and HIV-1 and HIV-2 antibodies. |
| Western blot (WB) | - No advantage and no longer recommended as a supplemental test method.
| - Results may be indeterminate and require repeat testing at a later time.
- Labor-intensive procedure
- Cost
- Requires skill and expertise to correctly perform and interpret the results.
| Should not be used as an initial assay due to lower sensitivity than immunoassays. |
| Nucleic acid testing (NAT) or Nucleic acid amplification testing (NAAT) | - Earliest detection of HIV infection in high-risk seronegative individuals.
- Can be used to detect infection in newborns born to HIV-positive mothers.
| - Specialized training required to perform the assays
- Dedicated laboratory equipment and space required
- False-negative results due to viral suppression are possible.
- False-negative results are possible due to improper specimen collection, improper processing, improper storage temperature, or interfering substances in the specimen.
- False-positive results are possible if technical errors occur (e.g., amplicon carryover, cross-contamination, inaccurate cutoff values).
| Preferred method for screening blood, plasma, and tissue products. The FDA and AABB require both antibody and NAT testing.
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