Evaluation of Quantification of HIV-1 RNA Viral Load in Plasma and Dried Blood Spots by Use of the Semiautomated Cobas Amplicor Assay and the Fully Automated Cobas Ampliprep/TaqMan Assay, Version 2.0, in Kisumu, Kenya

Abstract

dIn Kenya, HIV-1 viral load monitoring is commonly performed with the Cobas Amplicor using plasma specimens. Interest is growing in transitioning to real-time PCR (RT-PCR), such as the Cobas Ampliprep/Cobas TaqMan (CAP/CTM), using dried blood spots (DBS). Before implementation, direct evaluation of the two assays using DBS field specimens is required. This study compares the sensitivity, specificity, negative and positive predictive values (NPV and PPV, respectively), concordance, and agreement between HIV-1 viral load measurements using plasma and DBS specimens obtained from 512 HIV-1-infected pregnant females enrolled in the Kisumu Breastfeeding Study and tested with the Cobas Amplicor and CAP/CTM assays. The sensitivity and NPV of viral load detection in DBS specimens were higher with CAP/CTM (sensitivity, 100%; 95% confidence interval [CI], 99.1 to 100.0%; NPV, 100%; 95% CI, 59.0 to 100.0%) than the Cobas Amplicor (sensitivity, 96.6%; 95% CI, 94.3 to 98.1%; NPV, 58.8%; 95% CI, 40.7 to 75.4%). The PPVs were comparable between both assays when using DBS. The specificity of viral load detection in DBS specimens was lower with CAP/CTM (77.8%; 95% CI, 40.0 to 97.2%) than that of the Cobas Amplicor (95.2%; 95% CI, 76.2 to 99.9%). Good concordance and agreement were observed when paired plasma and DBS specimens were tested with both assays. Lower specificity with the CAP/CTM is likely due to proviral HIV-1 DNA amplification and lower detection limits with RT-PCR. However, the CAP/CTM has better sensitivity and higher throughput than the Cobas Amplicor. These findings suggest that DBS may be a suitable alternative to plasma when using RT-PCR, which could increase access to viral load monitoring in resource-limited settings.

Point-of-Care Cepheid Xpert HIV-1 Viral Load Test in Rural African Communities Is Feasible and Reliable

“…In resourcelimited settings, especially in rural areas, laboratory-based HIV-1 RNA testing remains challenging for many reasons, among them insufficient access to laboratory facilities, cold-chain management shortcomings, and inability to consistently provide for sample transportation (8)(9)(10). Delays in the reporting of results may also negatively impact the HIV treatment cascade (11)(12)(13).…”

Leukodepletion as a Point-of-Care Method for Monitoring HIV-1 Viral Load in Whole Blood

“…These differences were attributed to the interference of proviral DNA that remained significant with relatively low VL levels. In another study comparing plasma and DBS for VL quantification with CAP/CTM, cellular DNA interference was also shown (19). Not unexpectedly, the same problems with VL quantification in WB were found in liquid WB and DBS.…”

HIV-1 variability and viral load technique could lead to false positive HIV-1 detection and to erroneous viral quantification in infected specimens

“…13 Despite an elevated LOD due to the small sample volume in DBS, a high correlation in HIV-1-RNA quantification from paired DBS/plasma specimens has been reported using kPCR 22,45,46 and CAP/CTM v2.0. 52 It is known that DBS samples carry viral RNA and both proviral and unintegrated DNA, in contrast to plasma samples which contain only viral RNA. Amplification of proviral DNA from peripheral blood mononuclear cells could explain detectable HIV-1 nucleic acids using whole-blood or DBS specimens, even when corresponding plasma specimens have undetectable VL measurements or viraemia below the assay cut-off.…”