Dried Blood Spots and Plasma Separation Cards can Broaden Access to Molecular Testing for HBV, HCV and HIV

Abstract

Approximately 3.5 million people acquired HBV, HCV, or HIV-1 in 2022, and 340 million persons are infected with at least one of these three viruses, mostly in low- and middle-income countries (LMICs). Nucleic acid amplification tests (NAAT) are precise and sensitive tools for viral infection diagnosis, monitoring and sequencing. NAATs typically rely on plasma specimens, which can be challenging to collect, store and transport in LMICs, limiting the reach of NAAT testing in rural and other resource constrained settings where trained phlebotomists and/or a cold chain for preservation and shipping are not available. Alternative specimen types that can overcome this limitation include dried blood spots (DBS) and dried plasma prepared using the Cobas Plasma Separation Card (PSC). We performed a literature review of DBS and PSC use for NAAT of HBV, HCV, or HIV-1 to summarise their performance characteristics, relative advantages and disadvantages and potential to support expanded access to NAAT. DBS have been used extensively for HIV-1 diagnosis and viral load monitoring, as well as for HBV and HCV, albeit to a much lesser degree. Compared to plasma, DBS perform well in terms of accuracy but have lower sensitivity. There is a risk of low specificity due to the presence of cellular nucleic acids in DBS and a resulting over-estimation of viral load. The PSC has similar accuracy and sensitivity compared to DBS, but improved specificity due to the removal of cellular components. Both DBS and PSC have the potential to enhance access in populations where the use of plasma is challenging.

FIGURE 1

Comparison of steps for preparation of plasma, DBS and PSC. The steps required for specimen preparation when NAAT is indicated are shown. Both DBS and PSC can be prepared using capillary blood (e.g., form a finger prick) or venous blood following venipuncture. Nucleic acids extracted from DBS will contain relatively more DNA (illustrated as a double helix) versus RNA (single stranded). EDTA, ethylenediaminetetraacetic acid; PPT, plasma preparation tube; DBS, dried blood spot; O/N, overnight; PSC, plasma separation card.

FIGURE 2

Literature search results for DBS (A) and PSC (B). Additional details related to the reasons for exclusion can be found in the Supporting Information S1. DBS, dried blood spot; NAAT, nucleic acid amplification test; PSC, plasma separation card.

FIGURE 3

Examples of DBS preparation by pipetting (A) and drying in a rack (B). Photographs taken by NP in June, 2011 at the UVRI in Entebbe, Uganda [26].

FIGURE 4

Examples of PSC preparation by transfer pipette (A) and spotting with a syringe (B). Photographs taken by Dr. Camila Picchio, Barcelona Institute for Global Health (ISGlobal), Hospital Clinic, University of Barcelona, Barcelona, Spain and used with permission.