The laboratory will assume that consent for HIV testing has been taken when a signed or printed request form specifying HIV testing (either by ticking the box for HIV test or the word “HIV request” is written) is received in the laboratory before a HIV test is performed.
All telephone requests for addition of HIV testing in samples already in the laboratory must be referred to the consultant virologist (or to senior BMS if consultant virologist is unavailable). The details of the caller are recorded in the laboratory system and if testing is agreed, results should be suppressed and only verbal results will be dispatched to the person who asked for the HIV test. If a signed request form for HIV is received at a later stage, then a report can be issued.
All HIV testing is performed using the patient’s primary clotted blood tube.
HIV antigen/antibody screening test is performed on the Architect platform (4th generation ELISA).
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If the HIV screen test is negative, this should rule out HIV infection unless there was recent high exposure within the last 3 months (please contact consultant virologist if there was recent exposure or re-test in 3 months post high risk exposure).
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If the HIV screen is strong-reactive, a 2nd ELISA (4th generation) and Geenius test (to differentiate HIV-1 from HIV-2) follow. Also, an aliquot of sample will be sent to Colindale for an incidence test. Further samples will also be requested (as detailed below).
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If the HIV screen is weak-reactive, the laboratory will try to resolve the situation by testing for HIV on the 2nd platform (VIDAS), test for p24 antigen/p24 neutralisation (VIDAS), & perform HIV viral load. Further samples will also be requested (as detailed below).
HIV positive diagnosis sorted by origin of sample request
Hospital based patient/GP based patient (named patient): |
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Initial sample (named patient) |
HIV positive result should have two 4th generation ELISA & Geenius test. Laboratory will copy GUM (Lawson unit) in the report. The laboratory will phone results to the requesting doctor (hospital based or GP) with advising on GUM liaison/referral and also notifies health adviser. If the original request has other tests than HIV that may delay HIV reporting, laboratory may send an interim report once tests for HIV are finalised. Follow up samples will be requested |
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Follow up samples (most likely from GUM, coded) |
2x 5 mL bottles of clotted blood: one will be tested for HIV on Architect to confirm identity of patient sample, with an aliquot sent to Colindale* for incidence test, the other will be tested for baseline serology for HIV positive patients serology.
4 mL EDTA blood for HIV viral load. R |
GUM (Claude Nicol) based patient when HIV is picked up at routine GUM follow up (coded patient) |
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Initial sample (coded patient) |
HIV positive result should have two 4th generation ELISA & Geenius test. Aliquot of the sample will be sent to Colindale for incidence test. If the original request has other tests than HIV that may delay HIV reporting, laboratory may send an interim report once tests for HIV are finalised. Follow up samples will be requested. |
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Follow up samples (GUM, coded) |
2 bottles of clotted blood: one will be tested for HIV on Architect to confirm identity of patient sample, the other will be tested for baseline serology.
4 mL EDTA blood for HIV viral load. |
Transferred known HIV positive (Lawson unit). Please mark request as “transfer of care”. |
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Initial samples (coded patient) |
2 bottles of clotted blood: one will be tested for HIV (on two 4th generation ELISA & Geenius test with an aliquot sent for incidence test to Colindale), the other will be tested for baseline serology.
4 mL EDTA blood for HIV viral load. |
eferred to Virus Reference Department, Microbiology Services Colindale, 61 Colindale Avenue, London NW9 5HT
Out of hours/ on-call HIV testing