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Platelet aggregation with ADP
Medical expert of the article
Last reviewed: 05.07.2025
The processes of platelet aggregation are studied using an aggregometer, which reflects the course of aggregation graphically in the form of a curve; ADP serves as an aggregation stimulator.
Before adding the proaggregant (ADP), random oscillations of the optical density curve are possible. After adding the aggregant, oscillations appear on the curve due to changes in the shape of platelets. The oscillations decrease in amplitude, the optical density decreases. Platelets combine into aggregates and the curve deviates upward (primary wave). When the rise reaches a "plateau", a release reaction occurs, and the curve rises even more (secondary wave).
When exposed to small doses of ADP, a double wave of aggregation is recorded on the aggregogram. The first phase (primary wave) depends on the added exogenous ADP, and the second phase (secondary wave of aggregation) - due to the reaction of the release of its own agonists contained in the granules of platelets. Large doses of ADP introduced from outside (usually 1×10 -5 mol) lead to the fusion of the first and second waves of aggregation. To achieve double-wave aggregation, ADP is usually used at a concentration of 1×10 -7 mol.
When analyzing aggregograms, attention is paid to the general nature of aggregation (single-wave, two-wave; complete, incomplete; reversible, irreversible), the difference between the optical density of plasma before the onset of aggregation and after reaching maximum aggregation (characterizes the intensity of aggregation), as well as a decrease in the optical density of plasma during the first minute of aggregation or the slope of the curve at the stage of violent aggregation (characterizes the rate of aggregation). It is important to note that the appearance of two-wave aggregation upon stimulation with ADP and adrenaline in concentrations that normally cause reversible aggregation (usually 1-5 μmol) indicates an increase in the sensitivity of platelets to these inducers, and the development of single-wave incomplete (and often reversible) aggregation upon stimulation with them at concentrations of 10 μmol and more indicates a violation of the platelet release reaction. In clinical studies, the use of ADP in concentrations of 1×10 -5 mol (to achieve single-wave aggregation) and 1×10 -7 mol (to achieve dual-wave aggregation) is generally accepted.
Weiss aggregations for ADP
ADP, µmol |
Aggregations are normal,% |
10 5 2 1 |
77.7 66.1 47.5 30.7 |
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