Direct Processing and Storage of Cell-free Plasma using Dried Plasma Spot Cards

Abstract

Plasma separation cards represent a viable approach for expanding testing capabilities away from clinical settings by generating cell-free plasma with minimal user intervention. These devices typically comprise a basic structure of plasma separation membrane (PSM), unconstrained porous collection pad, and utilize either (i) lateral or (ii) vertical fluidic pathways for separating plasma. Unfortunately, these configurations are highly susceptible to (i) inconsistent sampling volume due to differences in patient hematocrit or (ii) severe contamination due to leakage of red blood cells (RBCs) or release of hemoglobin (i.e., hemolysis). Herein, we combine the enhanced sampling of our previously reported patterned dried blood spot (pDBS) cards with an assembly of porous separation materials to produce a patterned dried plasma spot (pDPS) card for direct processing and storage of cell-free plasma. Linking both vertical separation and lateral distribution of plasma yields discrete plasma collection zones that are spatially protected from potential contamination due to hemolysis and an inlet zone enriched with blood cells for additional testing. We evaluate the versatility of this card by quantitation of three classes of analytes and techniques including: (i) soluble transferrin receptor by enzyme-linked immunosorbent assay (ELISA), (ii) potassium by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and (iii) 18S rRNA by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). We achieve quantitative recovery of each class of analyte with no statistically significant difference between dried and liquid reference samples. We anticipate that this sampling approach can be applied broadly to improve access to critical blood testing in resource limited settings or at the point of care.

Hematocrit-independent sampling enables white blood cell counts from patterned dried blood spot cards

“…Based on our previous work, we expected that wax patterning DBS cards can enable reproducible sampling such that each zone can be treated as a replicate. 16,26 We chose to quantify the intracard and intercard reproducibility of volumes collected in punches obtained from 903 and pDBS cards. To measure the amount of whole blood in a dried punch, we generated reference curves at each hematocrit to correlate volumes of whole blood (0-20 µL) with absorbances at 540 nm utilizing Drabkin's reagent (Figure S2A).…”