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Platelet Aggregation 

  • Author: Christopher P Kellner, MD; Chief Editor: Thomas M Wheeler, MD  more...
Updated: Aug 01, 2014

Reference Range

The reference range is a normal biphasic pattern of aggregation in response to specific platelet activators (see image below).

Aggregation curve showing events in classic biphasAggregation curve showing events in classic biphasic aggregation.


Decreased platelet aggregation may be associated the following:


Collection and Panels

Specifics for collection and panels are outlined as follows:

  • Specimen type: Whole blood
  • Container: Vacutainer, light blue (citrate)
  • Collection method: Venipuncture
  • Specimen volume: 4 mL

Other instructions

See the list below:

  • Four tubes are needed for platelet aggregation testing.
  • Seven tubes are required for full aggregation and secretion testing.
  • Process whole blood specimens within 4 hours of collection.
  • Store specimens at room temperature (cooling may lead to activation).

Related tests: Complete blood count, platelet count, prothrombin time (PT); partial thromboplastin time (PTT), bone marrow biopsy, coagulation factors, von Willebrand factor (VWF)




Platelet aggregation studies test the clumping response of platelets to various platelet activators (eg, ADP, collagen, arachidonic acid, thrombin, epinephrine, ristocetin) as continuously recorded by a light transmission aggregometer. With some aggregometers, the secretion of platelet granules, another indicator of platelet function, may also be evaluated simultaneously by measuring the release of ATP by the aggregating platelets. Platelet secretion defects can provide greater diagnostic sensitivity than platelet aggregation testing alone.[1, 2, 3]


Conditions associated with decreased platelet aggregation include suspected hereditary and acquired disorders of platelet function. Indications for platelet aggregation studies include the following:

  • Diagnostic evaluation of excessive bleeding or bruising
  • Monitor the effectiveness of antiplatelet medication
  • Detect aspirin resistance
  • Monitor platelet function during complex surgical procedures
  • Screen at-risk presurgical patients


Medications (including over-the-counter medications) that may affect platelet aggregation results include the following:

  • Antibiotics (penicillins, cephalosporins, nitrofurantoin)
  • Antihistamines
  • Aspirin[4]
  • Aspirin-containing compounds
  • Clopidogrel[5]
  • Dipyridamole
  • Nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Theophylline
  • Ticlopidine
  • Tricyclic antidepressants

Healthcare providers should ask patients about any of these medications that may have been taken within 2 weeks before testing.

Contributor Information and Disclosures

Christopher P Kellner, MD Resident Physician, Cerebrovascular Research Laboratory, Department of Neurological Surgery, Columbia University Medical Center, New York Presbyterian Hospital

Christopher P Kellner, MD is a member of the following medical societies: American Association of Neurological Surgeons, American Medical Association, Congress of Neurological Surgeons

Disclosure: Nothing to disclose.

Chief Editor

Thomas M Wheeler, MD Chairman, Department of Pathology and Immunology, WL Moody, Jr, Professor of Pathology, Professor of Urology, Baylor College of Medicine

Thomas M Wheeler, MD is a member of the following medical societies: Alpha Omega Alpha, American Association for Cancer Research, American Medical Association, American Society for Clinical Pathology, American Society of Cytopathology, American Thyroid Association, American Urological Association, College of American Pathologists, United States and Canadian Academy of Pathology, International Society of Urological Pathology, Harris County Medical Society

Disclosure: Received stock from PathXL for medical advisory board. for: PathXL, Inc.


Judy Lin, MD

Disclosure: Nothing to disclose.

  1. Burris CA, Ashwood ER, Burns DE. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th ed. St. Louis: Elsevier Saunders; 2006. 1633:962-967.

  2. McPherson RA, Matthew R. Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia: Elsevier Saunders; 2011. 254-5.

  3. Wallach J. Interpretation of Diagnostic Tests. 6th ed. New York: Little, Brown; 1996. 717.

  4. Lee J, Kim JK, Kim JH, Dunuu T, Park SH, Park SJ, et al. Recovery time of platelet function after aspirin withdrawal. Curr Ther Res Clin Exp. 2014 Dec. 76:26-31. [Medline]. [Full Text].

  5. Arbel Y, Birati EY, Finkelstein A, Halkin A, Kletzel H, Abramowitz Y, et al. Platelet inhibitory effect of clopidogrel in patients treated with omeprazole, pantoprazole, and famotidine: a prospective, randomized, crossover study. Clin Cardiol. 2013 Jun. 36(6):342-6. [Medline].

Aggregation curve showing events in classic biphasic aggregation.
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