HIV Testing Technologies

Transcription

1 HIV Testing Technologies Katrien Fransen (ITM) BREACH symposium Breack out session 28/29 September 2012

2 Topics 3 rd and 4 th generation screening tests Window period (time delay for testing) New: specimen, SRT, home testing Quality assurance programme of SRT Preliminary conclusions/recommendations

3 HIV antibody testing for HIV diagnosis Screening test (EIA) and confirmation test (western blot or LIA) + control

4 FLOW CHART ARL HIV CONFIRMATIE STRATEGIE monsters doorgestuurd voor confirmatie EIA1 / EIA2 EIA1 - EIA2 - EIA1 + EIA2 + EIA s discordant Ag LIA Ag + Ag - LIA HIV1 + HIV2 - LIA HIV1 - HIV2 + LIA HIV + 1 LIA HIV Ind LIA HIV1 - HIV2 - Mogelijk seroconversi e: 2de staal vragen Negatief HIV 1 positief HIV 2 positief WB2 Ag Ag Vervolg pagina 2 WB2 + WB2 - WB2 ind Ag + Ag - Ag + Ag - HIV pos 10ml EDTA bloed voor differentiatie PCR HIV 1 positief Mogelijk kruisreactie : staal voor PCR vragen Mogelijk seroconversi e: 2de staal vragen Onbepaald resultaat: 2de staal vragen Mogelijk seroconversi e: 2de staal vragen Negatief

5 Vervolg pagina 1 LIA + Ag LIA HIV ind Ag - LIA HIV ind Ag + LIA HIV - Ag - LIA HIV - Ag + LIA HIV1 + Ag - LIA HIV1 + Ag + LIA HIV2 + Ag - LIA HIV2 + Ag + LIA HIV + Ag - LIA HIV + Ag + Onbepaald resultaat 2de staal vragen Mogelijke seroconversi e 2de staal vragen Negatief Mogelijke seroconversi e 2de staal vragen HIV 1 positief HIV 1 positief HIV 2 positief HIV 2 positief WB2 1 Legende EIA1 = Enzygnost Anti-HIV 1/2 Plus EIA2 = Vironostika HIV Uni-Form II Ag/Ab LIA = INNO-LIA HIV I/II Score Ag = INNOTEST HIV Antigen mab WB2 = NEW LAV BLOT II Verklaringen EIA s discordant = EIA1+ / EIA2 - of EIA1 - / EIA2 + LIA HIV Ind = LIA HIV1 ind of LIA HIV2 ind of LIA HIV1 /HIV2 ind

6 Enzyme linked immunosorbent assays (ELISA) 1 st generation sensitivity increase Purified HIV lysates 2 nd generation Recombinant proteins and/or synthetic peptides 3 rd generation or sandwich ELISA s Labelled antigen as conjugate 4 th generation or DUO assays Detect Ag and Ab without differentiation 5 th generation or DUO assays Detect Ag and Ab with differentiation 6

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8 Seroconversion panels Commercial: subtype B, variable bleeding time points of each of the panel members Time between detection of RNA and Ag test: Time between detection of RNA and 4 th generation test: Time between detection of RNA and 3 rd generation test: 0-12 days 0-18 days 0-26 days Clinical trial Prep panels: non-b subtypes, fixed time points (4 weeks). Unpublished data. Time between detection of RNA and Ag, 4 th, 3 rd generation test: 0-4 weeks or 28 days

9 Belgian guidelines (update 2011) -Serological test 4-8 weeks after suspected contact, repeat after 3 months and for medicolegal reasons after 6 months (prof exposure). If primary infection is suspected, perform the test immidiately and inform the laboratory.

10 Pro for keeping the 3 months. - Not many studies, data to answer that question (prep studies) (recomm) - 20% of the periferal laboratories are still not using 4 th generation test (recomm) - Analytical sensitivity of the p24 Ag varies ( pg/ml), no HIV 2 - Not all the patients are telling the thruth about risk and time of the risk Risk perception is not well known (recomm) - The laboratory is not allways informed about the recent risk and therefore an Ag test is not performed or asked (recomm) - Literature, on late seroconverters, second window period Conclusion: a test performed 3 months later will cover the missed diagnosis. Nevertheless according to the preliminary data of the seroconverters (subtype B and non B), we can assume that most of the hiv infections (99%?) will be detected within the period of 4-6 weeks after risk exposure. (if no ARV was taken)

11 Alternatives: Simple rapid tests - More than 100 different assays (WHO procurement list). Agglutination assays, Immunofiltration assays (flow through), Immunochromatographic assays (lateral flow through), Dipsticks. - Very few 4 th generation tests (CE label): 1) Determine TM HIV-1/2 Combo (Alere), 2) SD Bioline TM HIV Ag/Ab Combo test (Standard diagnostics) Attention: different sensitivities of the performance of the Ag (analytical, subtype and type specific). Is not well covered by the CE label, nor by the WHO panel. Additional evaluations/validations are needed. 11

12 Alternatives: Oral fluid tests (no Ag) - SRT (CE, FDA): OraQuick Advance Rapid HIV-1/2 Cons: expensive (40$), 3 rd generation, variable in quality? (NY), IQC and EQC? - ELISA: Genscreen, Vironostika, Enzygnost Oracol device to collect oral fluid, followed by an adapted protocol and cut-off calulation for screening. Broaden the reach of testing programs: outreach testing, epidemiological and surveillance studies 12

13 Alternatives: Home testing, self testing Pro Autonomy, less risks if status is known Cons Expensive, no proved, consistant quality, obscure companies, no CE label, ethical issues, link with care (for counseling and treatment)? But will be (is) used and we have to do more research on the usefulness of those tests especially in broadening the acces of people being tested. 13

14 EQC for SRT and OF tests Serum/plasma: existing EQC programmes (HIV ab/ag) Whole blood, capilary blood, oral fluid, saliva (urine): no existing EQC programmes. Organise an EQC using spiked serum in negative whole blood or negative oral fluid. Make a dilution series and use a week positive sample for lot control and/or internal control. Ask informed consent of the negative donors and mix several donors. A EQC can be prepared in the same way (blind).

15 Recommendation/conclusion -4 th generation screening test mandatory, -be aware of the existance of an Ag test -ARL guidelines 4-6 weeks, 3 months but develop a tool for self risk assesment -SRT and saliva test: reach vulnerable people, broadens access to HIV test. -self test, home test, home sampling: is used allready, expensive, questionable quality, best to have a link with an ARL for quality control and further testing and with an ARC for care for prevention and treatment. -> research