Blood typing, donor compatibility testing, and hematocrit analysis are blood tests performed to ensure the compatibility of the donor red blood cells (RBCs), plasma, or platelets with the transfusion recipient and to determine the need for transfusion. These tests are performed routinely prior to blood transfusions [1] and organ transplants [2], for the management of trauma patients [3], and for pretransfusion testing for conditions such as anemia, leukemia or surgical patients. Where centralized laboratories are available, blood samples are collected, transported, centrifuged to separate red blood cells (RBCs) from plasma, and then batched prior to evaluation using automated instruments. Nevertheless, the centralized/batched model can add minutes to hours to the test time, which is adequate for some patients but can be life-threatening for critical-care patients who need rapid testing results [4].

An alternative to centralized testing is the use of portable tests that can be performed directly on whole blood at the "point of care" (POC). Unfortunately, it is widely understood that user mishandling and misinterpretation of results is an Achilles' heel for these techniques [5–8], which has limited their use in medical settings. In sum, there are substantial limitations to both centralized and POC blood tests, which often leads healthcare practitioners to rely on blood products from “universal blood donors” (i.e. group O RBCs and group AB plasma). However, these products are in chronic short-supply and inventory levels are often below target levels worldwide [9].

As a step towards providing rapid results at the bedside, we developed a point-of-care hemagglutination system relying on digital microfluidics (DMF) a fluid handling technique that enables the manipulation of discrete liquid droplets on an array of electrodes [10]. We also developed a unique, automated hemagglutination readout algorithm. We validated our algorithm for rapid (<6 min) blood typing, donor compatibility testing, and hematocrit analyses on whole blood samples using an inexpensive shoebox-sized instrument. The system was then transported to a clinical setting, where it was operated by an inexperienced user, with results found to be 100% concordant with the gold standard technique. These results suggest great promise for our DMF platform to deliver rapid, reliable results in a format well suited for the trauma center and other settings where every minute counts.