review · PLoS Medicine
Standard plasma testing for HIV-1 viral load is difficult in resource-limited settings because of the requirement for cold storage and rapid transport. Dried blood spot specimens offer an alternative format, but their diagnostic performance across different testing platforms required systematic assessment. A meta-analysis of 40 studies comprising 10,871 paired dried blood spot and plasma samples evaluated the accuracy of commonly used viral load technologies. While dried blood spots consistently yielded higher mean viral load estimates than plasma, they performed best for identifying treatment failure at the World Health Organization threshold of 1,000 copies per millilitre. At this cut-off, five technologies achieved sensitivity above 95 percent, and five showed specificity above 85 percent, though two had specificity below 60 percent. Overall, dried blood spots provide a viable approach to expand treatment monitoring where cold chains are absent.
Routine viral load testing is essential to verify that antiretroviral treatments remain effective and to catch emerging drug resistance early. However, plasma testing requires reliable cold-chain transport that many clinics lack. Demonstrating that dried blood spot samples perform reliably against established clinical thresholds provides public health programmes with a practical, robust method to expand life-saving diagnostic services to remote and resource-limited clinics.
This evidence supports the scale-up and commercial deployment of dried blood spot collection kits and protocols for use with established viral load analysers by healthcare providers and national health systems. The application is applied and tested, but real-world commercialisation requires addressing variable platform specificity and verifying diagnostic performance using routine, field-collected blood spots rather than laboratory-pipetted samples.
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BACKGROUND: Accurate routine HIV viral load testing is essential for assessing the efficacy of antiretroviral treatment (ART) regimens and the emergence of drug resistance. While the use of plasma specimens is the standard for viral load testing, its use is restricted by the limited ambient temperature stability of viral load biomarkers in whole blood and plasma during storage and transportation and the limited cold chain available between many health care facilities in resource-limited settings. Alternative specimen types and technologies, such as dried blood spots, may address these issues and increase access to viral load testing; however, their technical performance is unclear. To address this, we conducted a meta-analysis comparing viral load results from paired dried blood spot and plasma specimens analyzed with commonly used viral load testing technologies. METHODS AND FINDINGS: Standard databases, conferences, and gray literature were searched in 2013 and 2018. Nearly all studies identified (60) were conducted between 2007 and 2018. Data from 40 of the 60 studies were included in the meta-analysis, which accounted for a total of 10,871 paired dried blood spot:plasma data points. We used random effects models to determine the bias, accuracy, precision, and misclassification for each viral load technology and to account for between-study variation. Dried blood spot specimens produced consistently higher mean viral loads across all technologies when compared to plasma specimens. However, when used to identify treatment failure, each technology compared best to plasma at a threshold of 1,000 copies/ml, the present World Health Organization recommended treatment failure threshold. Some heterogeneity existed between technologies; however, 5 technologies had a sensitivity greater than 95%. Furthermore, 5 technologies had a specificity greater than 85% yet 2 technologies had a specificity less than 60% using a treatment failure threshold of 1,000 copies/ml. The study's main limitation was the direct applicability of findings as nearly all studies to date used dried blood spot samples prepared in laboratories using precision pipetting that resulted in consistent input volumes. CONCLUSIONS: This analysis provides evidence to support the implementation and scale-up of dried blood spot specimens for viral load testing using the same 1,000 copies/ml treatment failure threshold as used with plasma specimens. This may support improved access to viral load testing in resource-limited settings lacking the required infrastructure and cold chain storage for testing with plasma specimens.
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DOI: 10.1371/journal.pmed.1004076
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