Both Coumatrak and CoaguChek Plus are based on the same method principle, utilizing a test cartridge containing rabbit brain thromboplastin, stabilizers, and preservatives. A single drop of whole blood (noncitrated) is added to the test cartridge inserted into the monitor. The blood travels by capillary action, mixes with thromboplastin in the reagent chamber, and continues to flow along a reaction track until a clot is formed. An optical laser monitors this blood flow, and the resulting time to clot formation is displayed in seconds; PT ratio and INR are also reported.
Each TAS PT-One test cartridge contains lyophilized thromboplastin from human placenta, calcium chloride, and buffers coated with paramagnetic iron oxide particles (PIOP). The citrated blood is added to the single-use test cartridge positioned within the TAS analyzer. A pulsating magnetic field is then initiated, causing the PIOP to move up and down. As the sample clots, the decrease in PIOP motion is detected and the resulting clotting time displayed. Each cartridge lot is magnetically encoded with an International Sensitivity Index (ISI) and a reference mean value, 0.99 and 12.2 s, respectively.