Coagulation
Coagulation laboratory tests
Platelet aggregation studies
Author: Jeremy C. Parsons, M.D.
Last author update: 1 November 2012
Last staff update: 23 September 2020
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Platelet aggregation studies [title]
Cite this page: Parsons JC. Platelet aggregation studies. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationplateletaggregation.html. Accessed June 5th, 2023.
Definition / general
- Used to assess platelet function if a familiar bleeding disorder is suspected, but the PT, PTT, platelet count and von Willebrand tests are normal (which is unusual)
- May include platelet responses to adenosine diphosphate (ADP), epinephrine, collagen and arachidonic acid
- Agglutination with ristocetin may also be assessed
- Usually 60% or more platelets aggregate with the above agonists, but not spontaneously; aggregation is decreased in newborns (Br J Haematol 1988;68:53)
- Note: testing is labor intensive and must be scheduled in advance because a normal control must be drawn simultaneously
- A platelet function assay (e.g. PFA-100) may be used to assess platelet function; although easier to perform, it is not as robust as platelet aggregation and must be interpreted with caution
- Hereditary disorders:
- Consider in patients with bleeding histories, no obvious acquired cause, but abnormal platelet aggregation study repeated at least once, same abnormality in family members
- May be a platelet storage pool disorder (deficiency in alpha or dense platelet granules), Glanzmann thombasthenia (deficiency of platelet glycoprotein IIb / IIIa, reduced aggregation by all agonists except ristocetin) or Bernard-Soulier disease (deficiency of platelet glycoprotein Ib, causes decreased ristocetin-induced aggregation only)
Laboratory
- Aggregometry with platelet-rich plasma to measure optical transmission or electric impendence (J Thromb Haemost 2009;7:1029)
- Whole blood aggregation with a lumiaggregometer can measure both aggregation and ATP release
- Abnormalities are often due to medications (aspirin - affects arachidonate aggregation; other platelet-inhibiting agents); also uremia, monoclonal gammopathy and myeloproliferative disorders
