Application of blood rheology to develop hemolysis-free serum extraction sampling method for small-volume blood

The growing demand for point-of-care testing (POCT) has increased interest in at-home blood testing. However, practical methods for obtaining serum from small-volume blood samples remain limited. This study investigated the effects of dilution buffers and additives on RBC aggregation and clot-formation behavior in diluted blood to develop a novel serum extraction method.

Residual blood samples obtained from outpatients were used to evaluate RBC aggregation and clot-formation behavior with various dilution buffers and additives, including polyethylene glycol (PEG). Based on effective combinations, a filtration-based method for serum extraction from small-volume blood samples was developed and evaluated.

Dilution with saline or phosphate-buffered saline resulted in large clots and numerous floating red blood cells (RBCs). In contrast, the high-molecular-weight PEG reduced clot size and markedly decreased the number of floating RBCs. Hypertonic dilution buffers also reduced floating RBCs without disrupting clot formation. By combining PEG with hypertonic buffers, serum was successfully extracted by manual filtration without hemolysis. The extracted serum enabled C-reactive protein measurement that strongly correlated with measurements obtained from conventional serum samples.

A simple and rapid method for hemolysis-free serum extraction from small-volume blood samples was developed using PEG and hypertonic buffers. This approach may facilitate the development of POCT applications requiring reliable serum collection from limited blood volumes.