Liquid Level Detection on a Coagulation Device

A coagulation analyzer is used to test a patient's blood clotting properties, which allows for the screening and assessment of bleeding disorders and the monitoring of anticoagulation therapy. Typically, a patient's plasma sample is used for the test. The plasma sample is obtained by centrifuging a whole blood sample to compact the red blood cells at the bottom of the vial and the plasma at the top. The buffy coat, which is less than 1% of the total volume of the blood sample, contains most of the white blood cells and platelets. The sample probe on the analyzer is used to aspirate a small volume of plasma from a vial. As the probe is lowered into the vial, the system needs to know when the probe contacts the plasma, at which point the probe stops moving. The probe is then lowered further into the plasma which ensures that the probe will aspirate plasma and not air. A liquid bubble or foam in the vial can falsely trigger the liquid-level detection system. The probe is then lowered too early and aspirates air and foam instead of plasma. This causes blood tests to produce incorrect results which can be problematic for patients and their treatments. The goal of this team was to improve the current LLD system to produce a 100% accuracy in liquid detection and plasma aspiration.