Acoustophoresis-based blood sampling and plasma separation for potentially minimizing sampling-related blood loss

Frequent blood sampling in vulnerable patient groups, such as prematurely born infants, can lead to significant blood loss and increased transfusion needs. Current pre-analytical technology requires comparably large blood volumes and leads to discarding of cells. This study investigates a device prototype enabling in-line sampling where cell-reduced plasma for clinical chemistry analyses is generated through acoustophoresis.

Blood samples were collected from healthy adult donors in lithium-heparin tubes without gel. Plasma separated via acoustophoresis was compared with centrifuged plasma (2000 g × 10 min) for cell counts (n=14), cell-free hemoglobin (n=21), and 12 routine clinical chemistry analyte tests (n=21). Wilcoxon signed-rank tests and Bland Altman analysis were used for statistical comparison.

Both acoustophoresis (AF) and centrifugation (CEN) generated cell-reduced plasma with<0.01 % of cells remaining after separation. However, compared to CEN plasma, more cells (median count per μL 642 vs. 205, p<0.01) and platelets (median count per μL 20,477 vs. 1,537, p<0.0001) remained in AF plasma. Cell-free hemoglobin (fHb) in AF plasma samples (range 0.0-0.2 g/L) was lower (p<0.01) than in CEN plasma samples (range 0.1-0.3 g/L). Statistically significant relative mean differences in test results ranging from 0.84 % (95 % CI 0.48-1.19) for sodium to 10.50 % (95 % CI 5.02-15.99) for AST were found.

This proof-of-concept study demonstrates that acoustophoresis has the potential to produce sufficiently cell-free plasma for several commonly performed clinical chemistry analyses. Further studies should assess pathological samples, platelet activation, and improve the design for more efficient removal of platelets.