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platelet aggregation measurement; platelet function analysis (PFA-100)

Indications: - personal or family history of mucocutaneous or postsurgical bleeding [2] Contraindications: - routine preoperative screening [2] Procedure: - citrated platelet-rich plasma is continuously stirred in a platelet aggregometer with a light beam passed through the suspension - platelet aggregation in response to added chemical stimulus is then monitored by changes in light transmittance. - a discoid to spheroidal shape change is seen as an initial decrease in transmittance & the subsequent platelet clumping allows more light to pass thus is recorded as an increase in light transmittance - some instruments are equipped with a 2nd channel to measure release of ATP from platelet dense granules - this is accomplished by addition of firefly luminescence substrate & enzyme (luciferin & luciferase) to the platelet-rich plasma - released ATP functions as a cofactor for light emission by luciferase - the emitted light is recorded by a 2nd photodetector - reagents used to stimulate platelet aggregation include: a) collagen b) epinephrine c) ADP d) ristocetin e) A23187 (a Ca+2 ionophore) f) arachidonic acid Clinical significance: - see bleeding time - effects of aspirin on platelets are irreversible - effects of other NSAIDs on platelets are reversible Specimen: - citrated platelet-rich plasma

Related

platelet aggregation; platelet function

Specific

platelet aggregation ADP induced platelet aggregation arachidonate induced platelet aggregation calcium ionophore induced platelet aggregation collagen induced platelet aggregation epinephrine induced platelet aggregation norepinephrine induced platelet aggregation ristocetin induced platelet aggregation serotonin induced platelet aggregation thrombin induced platelet aggregation thrombin receptor activating peptide-6 induced

General

clinical hematology test

References

  1. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 705
  2. Medical Knowledge Self Assessment Program (MKSAP) 16, 18. American College of Physicians, Philadelphia 2012, 2018.
  3. Panel of 5 tests Laboratory Test Directory ARUP: 30160
  4. Favaloro EJ, Lippi G, Franchini M. Contemporary platelet function testing. Clin Chem Lab Med. 2010 May;48(5):579-98 PMID: 20148722