Microrheological Method Determines Blood Type

The development of microfluidic blood-typing assays can reduce the time of analysis, and enable simultaneous determination of the most clinically important antigens.

A method for typing and subtyping blood has been developed in a simple microfluidic system that monitors the speed of flow of microdroplets and determining agglutination in small samples of liquid.

Scientists at the Institute of Physical Chemistry of the Polish Academy of Sciences (Warsaw, Poland) have demonstrated a microfluidic method for reproducible and objective determination of agglutination in small, nanoliter quantities of liquid. They demonstrated the reliability of the method on the model example of determination of blood type, yet the method should also be possible to use with the wide range of agglutination assays used in in vitro diagnostics.

The investigators tested agglutination in droplets with A, B and O blood groups, and then a second series of agglutination test in droplets with different Rh factors. Each series was performed for both standardized red blood cells and human blood samples. The red blood cells were not removed from the whole blood before these tests. In each series a droplet with antibodies was linked in the merging chamber with a droplet containing red blood cells. The merging chamber was equipped with two electrodes connected to a source of alternating current (AC) electrostatic potential. An oscillating electric field speeds up the coalescence of droplets arriving from the individual T-junctions. A created droplet was sent to the section of measurement for the time of flow.

The method had a very high sensitivity and reliability. The reliability approached 100% with an estimated chance of mistyping on the order of one per million samples. The method of detection of agglutination could potentially be used for automating various agglutination assays. The authors noted that the method offers the potential benefits of a reduction of the volume of blood sample to single microliters for the whole test, the lack of requirement for preprocessing such as centrifugation, and eliminating any subjectivity from the procedure.

Importantly, the method could be compliant both with a point-of-care format for the simplest blood-typing protocols and with multiplexed assays for complex analyses, such as cross-match testing or other multiple antigen determinations in a bench-top format. The study was published on June 18, 2013, in the journal Lab on a Chip.

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Polish Institute of Physical Chemistry