GTT2
In the GTT-2, blood flows under gravity during the whole measurement. The initial shear-rate is ~12,000s-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 d≥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 stabilisation period (default d≥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.


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 d≥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). 
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