Use of a Prequalification Panel for Rapid Scale-Up of High-Throughput HIV Viral Load Testing

Abstract

c Increased access to antiretroviral drugs expands needs for viral load (VL) testing. South Africa's National Health Laboratory Service responded to demands by implementing two testing platforms in 17 laboratories within 8 months. An industry partner's collaboration, training programs, and method verification with a VL prequalification panel ensured testing quality and rapid implementation.M ore than 1.4 million patients receive antiretroviral (ARV) treatment in South Africa through the public health services (1,8). In response to such demand, 17 HIV viral load (VL) testing laboratories were identified for the national HIV program between May 2010 and January 2011. These were distributed throughout the 9 provinces at both rural and urban laboratory centers. Several sites were newly implemented (n ϭ 6), and the remaining required minimal renovation to accommodate the new VL testing platform footprints. A total of 75 technical staff members were trained. Two viral load testing platforms were selected for implementation using a stringent tender-based procurement process. The first platform was the COBAS TaqMan HIV-1(CAP/ CTM) version 2.0 docked system (Roche Molecular Systems, Branchburg, NJ) (n ϭ 20), which combines the extraction of total nucleic acids on the COBAS AmpliPrep (CAP) with real-time PCR on the COBAS TaqMan analyzer (CTM). Each site with this platform also installed a preanalytical sample-handling P630 device (Roche), ensuring further automation. The second platform was the Abbott m2000sp (n ϭ 23) for nucleic acid extraction and the m2000rt for amplification and detection to perform the Abbott RealTime HIV-1 assay (Abbott Molecular Inc., Des Plaines, Illinois). Both automated systems are based on real-time PCR and were connected to the National Health Laboratory Service's (NHLS) laboratory information system (LIS). Both assays have been validated (4), including in-country validation (5, 7), and therefore did not require further validation but, rather, verification after platform placement to ensure adequate site performance. The verification was required within 1 week of installation to ensure each instrument was "fit for purpose" for clinical sample testing and result reporting.The material used to prepare the verification panels was a combination of known HIV-positive and -negative plasma packs (ϳ200 ml) obtained from the South African National Blood Services (SANBS). SANBS tests all plasma using the Procleix Ultrio blood donor screening test (Gen-Probe and Novartis Diagnostics, Emeryville, CA) to confirm positive or negative HIV status. Each pack was quantitated (using both assays at the NHLS Charlotte Maxeke Academic Hospital PCR reference laboratory in Johannesburg) and kept frozen (Ϫ70°C) until results were obtained by testing on both VL testing platforms in the reference laboratory in Johannesburg. The bulk plasma packs were then thawed in a 37°C water bath and diluted (using negative plasma) or pooled and aliquoted into 6 bulk lots calculated to produce a range of VL.Once manufactured, these b...

Options to Expand HIV Viral Load Testing in South Africa: Evaluation of the GeneXpert® HIV-1 Viral Load Assay

“…To verify the Xpert HIV-1 VL assay (referred to as Xpert VL) as ‘fit-for-purpose’ prior to clinical specimen testing, a standardised, 42 member, frozen, subtype-C plasma panel (termed the South African Viral Quality Assessment–SAVQA) [11], was included in the evaluation. The SAVQA panel consisted of 22 HIV-negative specimens and 20 HIV-positive specimens ranging from 750 to 21000cp/ml (2-4log cp/ml) and is designed to measure accuracy and precision.…”

Prospective Evaluation of Diagnostic Accuracy of Dried Blood Spots from Finger Prick Samples for Determination of HIV-1 Load with the NucliSENS Easy-Q HIV-1 Version 2.0 Assay in Malawi

“…Levels of acceptable variability were determined as Յ0.19 standard deviation (SD) and Յ0.3 bias, as described previously (17,18).…”

Laboratory Evaluation of the Liat HIV Quant (IQuum) Whole-Blood and Plasma HIV-1 Viral Load Assays for Point-of-Care Testing in South Africa

“…The Liat HIV Quant plasma assay demonstrated acceptable bias of Ͻ0.3 log copies/ml for the majority of VL values of Ͼ3.0 log copies/ml, with an overall acceptable percentage similarity CV of 2.7% compared to that of the Abbott RealTime HIV-1 assay and even better performance of 1.8% compared to that of Roche CAP/CTMv2. These are below the expected limit of 2.9% CV reported for the comparison between Roche CAP/CTMv2 and Abbott RealTime HIV-1 on the SAVQA panel (19). Twenty confirmed HIV-negative specimens all were reported as undetectable on both the Liat HIV Quant whole-blood and plasma assays.…”

“…Due to a limited number of Liat plasma cartridges available, 10 of 17 HIV-negative panel members were tested, and all (n ϭ 25) of the quantifiable panel members were tested on a Liat analyzer. The results generated by the Liat HIV Quant plasma assay were compared to published criteria (Ͻ35% coefficient of variation on untransformed data; Ͻ0.19 log copies/ml standard deviations [SD]; Ͻ0.3 log copies/ml bias; Ͻ2.9% similarity coefficient of variation [CV] [21]) determined previously for the Roche CAP/CTMv2 and Abbott HIV-1 RealTime HIV-1 platforms on this panel (19).…”

“…An evaluation matrix is presented in Table 1 outlining the various evaluation components. A 42-member frozen plasma verification panel (termed the South African viral quality assessment [SAVQA], developed by the South African National Priority Program in Johannesburg using HIV subtype C plasma for verifying newly installed Roche CAP/CTMv2 and Abbott RealTime HIV-1 platforms), which included several confirmed HIV-negative blood specimens obtained from SANBS (South African Blood Transfusion Services) (19), also was included in the evaluation matrix. The panel is designed to measure precision (intra-and intervariability) as well as carryover (instrument contamination) and the limit of the blank (i.e., to correctly identify all HIV-negative specimens).…”