Flowchart for HIV screening and confirmation (accessible version)
Updated 25 May 2022
Applies to England
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For reporting comments please use the results table and reporting comments for HIV.
1. Perform HIV infection screening with a combined antigen/antibody (Ag/Ab) assay: is HIV Ag/Ab detected or equivocal?
If no, report as HIV Ag/Ab not detected. End of laboratory pathway.
If yes, go to step 2.
2. Perform a second Ag/Ab assay and a HIV typing assay to confirm screening result: are both confirmatory tests detected?
If yes, depending on the result of the typing assay, either:
a) report result as HIV-1 detected
or
b) if HIV-2 detected or both HIV-1 and HIV-2 detected, refer to reference laboratory that undertakes HIV-2 serology and HIV-2 RNA testing for confirmation. If confirmed, report either HIV-2 infection or HIV-1 and HIV-2 infection as appropriate. End of laboratory pathway.
If no, go to step 3.
3. Are both confirmatory assays not detected?
If yes, report as inconclusive result and request repeat serology in 2 weeks. Go to step 6.
If no, go to step 4.
4. Is the second Ag/Ab assay detected and the typing assay not detected?
If yes, possible early infection. Request repeat serology in 2 weeks and an EDTA sample for HIV viral load. Go to step 8.
If no, go to step 5.
5. Is the typing assay detected and the second Ag/Ab assay not detected?
If yes, this is a highly unusual result. Discuss with a reference laboratory.
6. Perform repeat HIV screening and confirmation: is serology unchanged?
If yes, report as no evidence of HIV infection (false positive). End of laboratory pathway.
If no, go to step 7.
7. Is the screening assay now negative?
If yes, report as HIV Ag/Ab not detected. End of laboratory pathway.
8. Perform repeat HIV screening, confirmation and HIV-1 viral load: is serology unchanged, or typing assay now detected, and HIV-1 RNA detected?
If yes, report HIV-1 infection confirmed. End of laboratory pathway.
If no, go to step 9.
9. Is the serology unchanged or now not detected, and HIV-1 RNA not detected?
If yes, report as no evidence of HIV infection (false positive). End of laboratory pathway.