The table below summarizes the most commonly used HIV detection methods, highlighting advantages and disadvantages of each.
|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 test will be negative, if testing performed during the window period (between infection and a detectable immune response).
- Method is less sensitive if 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|
- Can detect HIV infection before antibodies are produced (between 14 and 22 days post-infection).
- Once antibodies begin to be produced, antigen diminishes below detectable levels.
|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, 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
- 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 (eg, amplicon carryover, cross-contamination, inaccurate cutoff values).
|Preferred method for screening blood, plasma, and tissue products|