Platelet aggregometry

Schematic representation of results of platelet aggregometry. The test substance is added to platelet-rich plasma at the point shown by the arrow. Time progresses to the right; an upward deflection of the curve represents a decrease in optical density due to platelet aggregation, allowing more light to pass through the solution. Three examples are shown: Curve A: A normal response to addition of ADP is shown, with a first and second wave (phase) of aggregation. Curve B: Only a first phase of aggregation is seen. This pattern is seen in platelets taken from a patient with a storage pool defect after addition of an intermediate dose of ADP. Curve C: No response. This pattern is seen in platelets from a patient with Bernard-Soulier syndrome after addition of ristocetin or in patients with Glanzmann thrombasthenia after addition of all agonists except ristocetin.