Reduced Platelet Response

Here is a message from Crystal Azevedo at Eastern Maine Healthcare:

Hi George,
Is an abnormal platelet response to low-dose ADP a significant finding in the setting of an intracranial hemorrhage? Also, the epinephrine-induced aggregation was somewhat sluggish, but not markedly abnormal. The testing was performed 6 months following the hemorrhagic event. Thanks for your help as always!

Hello, and thank you for your question. I agree that a reduced platelet aggregation response to ADP in a patient who has experienced an intracranial hemorrhage warrants follow-up with full aggregation studies. You’ll want to confirm the patient has been off aspirin and NSAIDs for at least ten days and use standard concentrations of ADP, collagen, arachidonic acid, and thrombin or thrombin receptor activation peptide (TRAP). Typical ADP concentrations are 5 to 10 mcM, collagen, 5 mcg/mL, arachidonic acid 0.5 mM, and thrombin at 1 unit/mL. Because responses are variable, I don’t recommend using epinephrine.

Although aggregometry results require individualized interpretation, in general a reduced response to ADP in the absence of drug therapy may indicate an inherited or acquired abnormality of the ADP receptor site, P2Y12, and a reduced response to arachidonic acid may indicate an abnormal platelet secretion (release) reaction, sometimes called aspirin-like disorder, involving one of the enzymes of the eicosanoid (prostaglandin) synthesis pathway. A poor secretion response to thrombin or TRAP may indicate storage pool deficiency. This may seem simple, but interpretation becomes complex when there are combinations of results.