The effect of thrombocytopenia on the determination of platelet aggregation.

Platelet aggregation has been widely assumed to be unmeasurable in thrombocytopenic samples. Using a sensitive differential self differential self-calibrating aggregometer, and standard aggregating agents, aggregation was measured in serially diluted platelet-rich plasma. Aggregation induced by ADP or collagen was reproducible at platelet counts as low as 50,000 per cu. mm., and with epinephrine aggregation was reproducible at platelet counts as low as 75,000 per cu. mm.