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Volumetric microsampling devices (Figure 2.1) aim to collect a fixed volume of capillary blood, which can then either be made available for analysis in its entirety or can be used to provide a fixed volume of plasma for processing. These devices promise advantages over DBS related to sampling volume accuracy, simplified sample pre-treatment, and ease of automation (John et al., 2016).

Figure 2.1 Volumetric blood microsampling devices. (a) Mitra (Neoteryx) uses an absorptive pad to collect a fixed volume of blood; (b) HemaXis DB uses a fixed volume capillary to transfer blood to a standard DBS card

Volumetric absorptive microsampling (VAMS^®) aims to absorb a fixed volume of blood or other fluid (10 or 20 μL) using the Mitra^® (Neoteryx) device (Spooner et al., 2015; Protti et al., 2019). Although some aspects still need to be investigated in depth (Kip et al., 2017), VAMS^® may be a viable alternative to DBS. It simplifies sample collection and storage, and may allow sample collection in a patient's home (Kok & Fillet, 2018). The HemaXis^TM DB 10 (DBS System SA) uses microfluidics to provide 10 μL whole blood from a reservoir onto a DBS card (Leuthold et al., 2015; Verplaetse & Henion, 2016). The HemaXis^TM DX promises to produce plasma or serum without the use of a centrifuge, filtration membrane, or pump and with no haemolysis. The resulting sample can be stored in dried or liquid format. The Noviplex™ Plasma Prep Card gives a fixed volume of plasma from a reservoir of whole blood (Heussner et al., 2017).