Platelet Aggregometry

Platelet aggregometry involves a series of tests performed on whole blood or platelet-rich plasma, using several agonists (platelet activators). The agonist is added to the suspension and a dynamic measure of platelet clumping is recorded. Simultaneously to platelet aggregation, luminometry test can be performed. In that case, ATP release is assayed using a luminescent marker.

The most common aggregation agonists are:

  • Arachidonic acid: used to assess the viability of the thromboxane pathway.
  • Thrombin: reacts with several membrane sites to induce full aggregation and secretion of organelle contents independent of the prostaglandin or ADP pathways.
  • ADP: binds to a specific platelet membrane receptor and causes platelet activation and release of dense granule stored ADP. Shows biphasic aggregation.
  • Epinephrine: binds to specific receptor and causes ADP secretion, but does not cause aggregation in storage pool disorder or release defects.
  • Collagen: Shows no primary wave of aggregation and depends on intact membrane receptors, membrane phospholipase pathway integrity and normal cyclooxygenase and thromboxane pathway function.
  • Ristocetin: requires vWF and intact surface membrane including a functional vWF receptor site (GPIb).

Typical aggregation tests using platelet-rich plasma requires a photometer with cuvette equipped with a stir bar and warmed to 37ºC. Aggregating agent is added and changes of optical density are plotted to view the aggregation curve.

The following animation is available for further details:

 Optical Aggregation in Platelet-Rich-Plasma

Selected profiles of the aggregation curve in platelet-rich plasma obtained using several agonists at different concentrations (AA: arachidonic acid; C: collagen). Click on picture to enlarge.

(Plots have been kindly provided by M. Pino. For image use, please see Use of Content at Legal Information).

Bibliography

Born GV. Aggregation of blood platelets by adenosine diphosphate and its reversal. Nature. 1962; 194: 927-9. 10.1038/194927b0.54      

Cattaneo M, Hayward CP, Moffat KA, Pugliano MT, Liu Y, Michelson AD. Results of a worldwide survey on the assessment of platelet function by light transmission aggregometry: a report from the platelet physiology subcommittee of the SSC of the ISTH. J Thromb Haemost. 2009; 7: 1029. 10.1111/j.1538-7836.2009.03458.x.

Gresele P, Harrison P, Bury L, Falcinelli E, Gachet C, Hayward CP, Kenny D, Mezzano D, Mumford AD, Nugent D, Nurden AT, Orsini S, Cattaneo M. Diagnosis of suspected inherited platelet function disorders: results of a worldwide survey. J Thromb Haemost. 2014; 12: 1562-9. 10.1111/jth.12650