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

Indications

• personal or family history of mucocutaneous or postsurgical bleeding

Contraindications

• routine preoperative screening

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

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:
  • collagen
  • epinephrine
  • ADP
  • ristocetin
  • A23187 (a Ca+2 ionophore)
  • arachidonic acid

More general terms

• clinical hematology test

More specific terms

• 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

Additional terms

• platelet aggregation; platelet function

Patient information

platelet aggregation measurement patient information