Point of Care HIV Viral Load Testing:

Transcription

1 Point of Care HIV Viral Load Testing: Lesley Scott, Natasha Gous, Shuqi Chen *, Wendy Stevens Department of Molecular Medicine and Haematology University of the Witwatersrand, National Health Laboratory Service National Priority Program Johannesburg, South Africa *IQUUM, Marlborough, MA, USA

2 CD4: for staging and monitoring HIV patients prior to initiation onto ART. Viral load testing: Identify early virological failure and target non-adherents Identify late failure for therapy switch Measure programme performance Diagnosis of acute infection Early Infant Diagnosis <18 m, DNA PCR (performed on viral load platforms). Need to increase access in resource-limited settings. Demand to simplify and improve efficiencies of these diagnostics without diminishing the quality of patient care. Source: UNITAID HIV/AIDS Diagnostic landscape, M.Murtagh 2012

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4 POC VL instrument Quantitative Fully automated Lab in a tube technology Sample extraction by magnetic silica beads Real-time detection LOD: 81 cp/ml in plasma, Dynamic Range: x10 6 c/ml Sample types: Blood 75ul Plasma 150ul TAT: Blood 35 minutes Plasma 30 minutes

5 1. Skilled personnel ~5-6 hours 2. Class II safety cabinet 4. Amplification and detection ~30 minutes 3. Fully equipped lab with separate rooms

6 Source: IQUUM Inc. Step 1. Add Sample Step 2. Scan Liat tube barcode Step 3. Insert Liat tube Step 4. Wait ~30 minutes for result All assay reagents pre-packed in Liat tube Internal control = RNA phage Tube is segmented by peelable seals Sample added to tube Sample processing actuators in the Analyser cause compression of tube to selectively release reagents and move the sample from one segment to another

7 3x instruments shipped and self installed Aug 2012 Blood specimens obtained from HIV+ consenting patients Hillbrow clinic 1x EDTA tube CHRU clinic 4x EDTA tubes Couriered to lab and LIAT testing performed on same-day Analysis: Accuracy, precision, linearity Qualitative: ease of use, # of invalids, # tested/day Comparator assays: COBAS AmPliprep/COBAS Taqman V2.0(Roche) Abbott Realtime HIV-1

8 Blood specimens from Hillbrow clinic Blood and plasma Range of VL tested per instrument Accuracy and limit of blank Bulk HIV+ plasma serially diluted with HIV- plasma Across 6 dilutions from 6log cp/ml to 1log cp/ml Each dilution tested over one day triplicate + testing Linearity and dynamic range and limit of detection Log ranges: log2.7, log3.7, log4.7 HIV positive patient bleeds from CHRU 3 samples in relevant range selected Analysed 6 times in one run across 3 instruments Precision

9 Comparison: TND or LDL on any assay: Roche n=36/121 (29%) Liat plasma n=36/121 (29%) Liat wb n=15/79 (18.9%) Abbott n=12/57 (21%) Assay N= Log mean c/ml Log Median c/ml Roche Abbott Liat plasma Liat wb

10 Bland Altman difference plot of Roche CAP/CTM versus: LIAT plasma, LIAT whole blood Abbott RealTime Bland Altman % Similarity Assay n= mean SD mean SD CV Roche CAP/CTM Versus Liat plasma Liat Blood Abbott plasma Abbott Realtime Versus Liat Plasma Liat Blood

11 Inter variability: stable over log range Intra variability: less precise at lower log range, as expected Outlier: instrument dependent Clinically relevant range = log 3 Majority above log 3 and within acceptable SD of 0.2 A total SD of <0.3SDcp/ml is acceptable at all VL ranges

12 Ease of use: Training and installation = ~1-2hrs No adverse events experienced by operator # of invalids: Liat tube scanning errors n=7 Solution: rescan tube # tested per day: ~12-14 specimens/8 hour day

13 Overall good performance (accuracy and precision) of LIAT compared to predicate technologies. Whole blood assay less variable in the lower VL log range may have advantage for infant diagnosis Plasma well suited to monitoring VL but requires centrifugation Easy to operate No laboratory skill required Full connectivity Small sample volume requirements (suited to finger stick) Short turnaround time Pipeline: LIAT Workstation 8 samples per run Compatible with EQA material Disadvantages: Cold storage required for reagent tube Next phase: Clinical evaluation

14 IV III 3ry Referral II District Hospital Health Post or Health Ctr Community health care re-engineering model I Level IV: National/multi-country reference lab Staff: Senior Health Specialist / lab management Dx: HIV resistance testing, HIV viral load, EID PCR, ELISA, AFB susceptibility Level III: Regional provincial Lab Staff: Lab specialists, senior techs, Programme officer Dx: Quantitative HIV (PCR or bdna), qualitative EID PCR, ELISA Level II: District lab Staff: Lab specialists, senior techs, Programme officer Dx: HIV serology by ELISA, other ELISA, CD4 count, basic chemistry, haematology & microbiology Level I: Primary Lab Staff: Doctors, Nurses, lab or Medical assistants, phlebotomists Dx: HIV rapid tests, other point-of-care tests* and DBS collection Sample collection (including DBS), preservation fluid *Malaria RDT, Glucometer, HemoCue Hb, Pregnancy test, Urine strip, Syphilis RDT, Lactate Accutrend, Reflotron, PIMA Ref:

15 A model for evaluating new and existing POCT in South Africa in partnership with developers and clinicians to interface with laboratory networks Testing parameter * Indication Platforms CD4 ART eligibility Pima (Alere) Needs assessment: HIV/TB treatment initiation and monitoring, based on SA guidelines Hb Detect anaemia Hemocue (Quest Diagnostics) Instrument selection and validation: literature, lab validation, field testing at POC Develop the package : site needs, SOP, training, implementation, QC, EQA, biosafety, connectivity, provide the clinical staff and obtain ethics and other approvals Cost evaluation, placement model within the tiered laboratory structure ALT, creatinine TB (active infection) Viral load* ART Toxicity monitoring, Identify coinfection ART monitoring Reflotron, (Roche) Xpert MTB/RIF (Cepheid) Sample collection potential candidates Policy recommendation

16 The National Health Laboratory Service and the NPP (esp Sergio Carmona and the PCR laboratory) The University of the Witwatersrand Sr Matilda Nduna, participants and staff at Hillbrow CHC Lara Noble and Pam Horsfield Funders (USAID, GCC, CDC, Pepfar) Clinical Partners (esp. Dr Andrew Black from WRHI, CHRU/RTC, PHRU) Contract laboratory services Shuqi Chen, Yu Tian and the IQUUM team