4 alternatives to dried blood spot cards
by Neoteryx | 2 min read
Dried blood spot (DBS) blood collection techniques have long been salient in blood analysis research. They can reduce costs, and they provide ethical advantages and higher sample retention.
However, DBS cards are not without limitations. Hematocrit level, blood viscosity, analyte nature, and sampling conditions all affect the blood sample analysis, particularly from an analytical standpoint.
Any thoughtful consideration of DBS techniques includes exploring popular alternatives. Here are four you should know about.
Solid Phase Microextraction (SPME)
Solid phase microextraction is a sample preparation method that is based on the differential migration of analytes from the sample fluid into the stationary phase: the functionalized silica particles, coated on a BioSPME metal fiber. The method is viable for direct sampling of whole blood, and also for urine, saliva, and tissue.
SPME technique combines sampling, sample preparation, and extraction in one step, reducing blood handling, as well as increasing speed, improving efficiency, and boasting high sensitivity, especially in regard to the influence of blood hematocrit on analysis.
The efficiency of the method is, however, still affected by sample properties. And while SPME is suitable for on-site use, the whole process, unlike DBS, needs to be carried out by trained medical personnel.
Pre-cut Dried Blood Spot (PCDBS)
Another technique that was developed to reduce the limitations of DBS, mainly the impact of hematocrit, is pre-cut dried blood spot (PCDBS) microsampling. Instead of using a partial, fixed-sized punch from a DBS sample, PCDBS is based on the whole sample analysis through accurate volumetric applications of blood onto a pre-punched disc. Other advantages of this sampling method include 100 percent sample utilization, further reducing the needed volume of blood and elimination of carryover concerns related to DBS sample punching workflow.
While well-suited for use in a controlled setting, the PCDBS technique is not yet viable for patient self-sampling situations due to a defined volume of blood required.
Dried Plasma Spot (DPS)
With the development of multi-layer collection membranes, the dried plasma spot (DPS) microsampling technique is carried out with ease and comfort of DBS, without the drawbacks of SPME and PCDBS (no need for a controlled environment), as well as challenges of whole blood analysis (impact of hematocrit).
The technology utilizes a two-layer sampling card, consisting of a separation and a collection polymeric membrane. The plasma from a drop of blood from a finger-stick prick can flow through the separation membrane, forming a plasma spot on the bottom collection membrane after the top layer is peeled off.
Volumetric Absorptive Microsampling (VAMS)
Volumetric absorptive microsampling (VAMS™) is a technique that allows the collection of volumetrically accurate samples of blood without the need for specialized devices.
The Mitra® microsampler consists of a plastic handle with an absorbent tip, with highly reproducible internal porous volume. The tip, when dipped into the sample, wicks up an accurate volume of blood independently of hematocrit. The whole VAMS tip is extracted without manipulation, providing further advantages over DBS (no punching), while still being fully viable in self-sampling or low-resource scenarios.
The method is also compatible with tip-based automation systems, making it an increasingly fruitful sampling technique from an analytical point of view.