In the GTT-2, blood flows under gravity during the whole measurement. The initial shear-rate is 12,000–14,000 s-1 . The rate of flow is expressed by the time-interval [d] between the consecutive blood drops. As shown in the graph below, initially [d] is small but increases as flow rate is reduced by the formation of thrombi in the gaps. When [d] reaches the level set in the instrument program (default 15 sec), “Occlusion Time OT” is displayed. The number of blood drops from OT until complete arrest of flow indicates thrombus stability at atmospheric pressure. There is a thrombus stabilization period (default 300 sec) during which the photosensors are inactive. After this stabilization period, the first drop of blood detected by the photosensor indicates the beginning of spontaneous thrombolysis (Lysis Time; LT). At atmospheric pressure the rate of thrombolysis is slow.

GTT-2 software (optional) graphic display of measurement

Definition of measured parameters
  • Occlusion Time (OT) - the time taken for start of thrombus growth, taken as the time when the time-difference between two consecutive blood drops [d] exceeds the time set in the Menu (default 15 sec).
  • Thrombus stability – this is defined by the number of blood drops from OT until the blood flow is arrested (X). X is inversely related to stability of thrombi grown at atmospheric pressure.
  • Lysis Time (LT) - the time (T1) from the start of the test until the first blood drop is detected after complete occlusion minus the time of OT (T2). LT= (T1) – (T2).