A new type of combination testing that can more accurately detect HIV infection based on testing of serum or plasma specimens is recommended. Prior guidelines utilized tests for only HIV antibodies, but the updated recommendations also include tests for HIV antigens and HIV nucleic acid. This is supported by studies conducted in high-risk populations for HIV that show antibody testing alone might miss a considerable percentage of HIV infections detectable by virologic tests.
The updated recommendations are based on HIV tests approved as of December 2012 and scientific evidence, laboratory experience, and expert opinion compiled from 2007 through December 2013. Some benefits over previous recommendations include:
- More accurate laboratory diagnosis of acute HIV-1 infection
- Equally accurate laboratory diagnosis of established HIV-1 infection
- More accurate laboratory diagnosis of HIV-2 infection
- Fewer indeterminate results
- Faster turnaround time for most test results
Testing is to begin with a combination immunoassay that detects HIV-1 and HIV-2 antibodies and HIV-1 p24 antigen. All reactive specimens on this initial assay undergo supplemental testing with an immunoassay that differentiates HIV-1 from HIV-2 antibodies. Then specimens that are reactive on the initial immunoassay and nonreactive or indeterminate on the antibody differentiation assay go on to HIV-1 nucleic acid testing for resolution. The HIV-1 Western blot and HIV-1 IFA that were previously recommended are no longer part of the new algorithm.
This algorithm may help identify patients likely to benefit from treatment, provide assurance to those who are uninfected, and provide evidence in reporting HIV infection to public health authorities.
These recommendations do not include the rapid HIV-1/HIV-2 antigen/antibody combination test approved by the FDA in August 2013 or HIV-2 nucleic acid tests, which are not FDA-approved.
For more information read the full guidelines at CDC.gov.