POCT HIV

Purpose:
Human immunodeficiency virus (HIV) is a retrovirus that preferentially infects and destroys cells of the immune system, in particular the CD4 cells (a class of T cells). Although significant progress has been made in the UK to reduce the incidence of HIV, there is a clear ambition to eliminate the viral transmission through the testing of all undiagnosed HIV and commencement of antiretrovirals (ARVs). A number of guidelines have been produced over the last few years including NICE guideline [NG60], HIV Testing: increasing uptake among people who may have undiagnosed HIV, NICE Quality Statement [QS157], HIV testing: encouraging uptake, HIV: testing at registration (IND210), the British HIV Association (BHIVA)/British Association for Sexual Health and HIV (BASHH)/ British Infection Association adult HIV testing guidelines 2020 to encourage testing including the Pre-exposure prophylaxis (PreEP) HIV prevention strategy and the BHIVA guidelines for the management of HIV-2, 2021.

BHIVA/BASHH/BIA adult HIV testing guidelines 2020.
Recommendations include testing groups at increased risk of exposure; HIV opt-out testing for people attending sexual health services, addiction and substance misuse services, antenatal, termination of pregnancy, services for hepatitis B and C, TB and lymphoma and patients commencing chemotherapy or immunosuppressive therapy; people presenting with symptoms; patients accessing primary and secondary healthcare in areas of high seroprevalence including emergency departments; sexual partners of those diagnosed with HIV. They also recommend that rapid community testing including Point of Care testing (POCT) increases testing rates in at-risk groups and should be commissioned as part of local HIV testing programmes.

PrEP is a HIV prevention strategy in which HIV-negative people use HIV (ARVs), drugs usually used to treat HIV infection, to reduce their risk of becoming infected with HIV. This service is available in the UK through the NHS sexual health clinics and requires HIV testing prior to receiving ARVs to confirm negative status. POCT HIV rapid testing, both 3rd and 4th generation are now widely available in the UK.

BHIVA guidelines for the management of HIV-2, 2021. Summary: Diagnosis of HIV-2 infection
Laboratory diagnosis of chronic HIV-2 infection
• Initial diagnosis of chronic HIV-2 infection should be made using a total of three CE-marked serology tests (i.e. tests conform to EU health and safety requirements) performed in an ISO 15189-accredited laboratory. There must be reactivity in two CE-marked fourth-generation tests for HIV-1 and HIV-2, followed by differentiation of HIV-2 by a third CE-marked antibody-only test. (Grade 1A)
• Clinicians should consider revisiting a previous diagnosis of HIV-1 by repeating HIV-2 serology and molecular tests in individuals with an undetectable HIV-1 viral load in the absence of ART, but a falling CD4 count. This is in order to detect the possibility of missed HIV-1 and HIV-2 dual infection. (GPP)
• Similarly, in those with diagnosed HIV-2 with an undetectable viral load in the absence of ART, clinicians should consider repeating HIV-1 diagnostic tests, if their CD4 count falls. This is to investigate the possibility of HIV-1 superinfection. (GPP)
Laboratory diagnosis of acute primary HIV-2 infection
• Investigation for acute or very recent HIV-2 infection should start as for diagnosis of chronic HIV-2 infection. A negative HIV-2 screening result on a blood weeks and 3 months, with parallel testing for HIV-2 viral RNA and, if necessary, HIV-2 proviral DNA. (Grade 1A)
Indeterminate HIV-1 or HIV-2 serology: how to investigate further
• Any HIV-1 or HIV-2 serology that does not fit into a clear pattern of a confirmed laboratory diagnosis is fully investigated for the presence or absence of HIV-2 infection, and that this should be established by PCR for HIV-2 proviral DNA. (Grade 1A)

Scope:
The Weqas POCT HIV Programme was specifically developed for 4th generation serology assays used in a POCT setting; to assess the user’s ability to correctly identify both HIV Antibodies and Ag, and assess the diagnostic accuracy of the methods using samples mimicking the different clinical presentations. HIV-1 p24 antigens are found on the surface of HIV cells approximately 12 to 26 days after exposure and before HIV antibodies are produced, allowing for earlier detection of the virus.

The sample matrix is ‘off the clot’ human serum tested negative for HIV, Hepatitis B and C at donor level which is spiked with a non-infective source of recombinant HIV markers (p24 Ag, HIV-1 Ab and HIV-2 Ab) at varying concentrations. Three samples are distributed bimonthly.

Performance Assessment The programme is designed to assess both user and method performance, including limit of detection, sensitivity and specificity. The scores broadly reflect clinical importance, where a correct result (in agreement with interpretive comment) is given a score of 0. A score of 3 or 4 is assigned for incorrectly identified results, where 4 represents a gross misclassification of the result. A negative result for a positive sample is given a score of 3 to 4 depending on the concentration of the positive sample. A positive result for a negative sample is given a score of 3.

Key Features:

Liquid human serum samples require no pre-analytical preparation.
Samples are prepared with a non-infective source of recombinant HIV markers (p24 Ag, HIV-1 Ab and HIV-2 Ab) to mimic different clinical presentations.
Developed for 4th generation assays, the user’s ability to identify both Abs and Ag are assessed.
Simple qualitative reports for end users.