The most conventional and widely used blood sampling method for research purposes is venipuncture (usually from the main veins inside of the elbow). However, this approach may cause distress for the volunteers entering the various types of clinical trials. The sampling also requires professional nurses and often recurring visits to the research facilities for the volunteers participating in the studies. To overcome these challenges various other approaches for blood collection have been developed.
With the collection of blood micro samples (BµS), less than 100 µL of sample is collected usually with less invasive punctures from fingertips or heels. BµS can be used to understand human health, as an alternative to plasma and serum, conventionally analyzed from large amounts of blood. Among the reported advantages of the BµS: i) they are more convenient for vulnerable groups such as the elderly and newborns as they are minimally invasive and allow a more frequent collection of multiple samples, ii) patients themselves can collect the samples and send them for analysis, and iii) Samples can be easily stored and transported, and are stable, especially most of them which are dry, being less susceptible to degradation or contamination.
Due to its advantages BµS, it is possible to find multiple options in the market, from Dried Blood Spots (DBS), used since 1961 for screening and detection of disorders like Phenylketonuria in Newborns, to volumetric and quantitative devices that absorb fixed volumes of samples. Consequently, interest in BµS continues to increase. Studies have shown their potential in clinical studies for disease biomarker identification, biological pathway understanding, and targeted studies of metabolites, lipids, peptides, and proteins.
The new devices promise to overcome the limitations of DBS, especially the “hematocrit bias” or “hematocrit effect”. The sample’s hematocrit values lead to uneven distribution of the blood samples on the filter papers and unwanted differences in the metabolite concentrations when the filter papers are further processed. The hematocrit effect is related to the viscosity of the blood collected on the filter paper, for example, samples with high hematocrit levels (higher red blood cell volume of the sample), will usually result in smaller spots.
From 2023 we are part of the HUMAN project (human-dn.eu). We will contribute to the project by optimizing an analytical method to do untargeted metabolomics on DBS and two BµS volumetric devices: Volumetric Absorptive Microsampling Neoteryx Mitra®, and Capitainer®. We will compare the metabolomic coverage between the BµS, plasma, and whole liquid blood, and at a further stage, we will assess the impact of lifestyle (diet and exercise) interventions on the blood metabolome using BµS.
Dennisse Avella
Topi Meuronen