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Diurnal variation in platelet aggregation iwth the PFA-100 platelet function analyser
M C Dalby1, S J Davidson, J F Burman
1Department of Cardiology, Royal Brompton and Harefield NHS Trust, London, UK. milesdalby@hotmail.com
Platelets
|November 18, 2000
Summary
Platelet aggregation shows a diurnal rhythm, with function increasing throughout the day. This study used whole blood at high shear rates, offering more relevant insights into in vivo conditions than prior research.
Area of Science:
- Cardiovascular Science
- Hematology
- Chronobiology
Background:
- Myocardial infarction incidence peaks in the morning.
- Previous studies on diurnal platelet aggregation used limited methods (optical aggregometry, low shear).
Purpose of the Study:
- To investigate diurnal variation in platelet aggregation using whole blood at high shear rates.
- To assess platelet function changes throughout the day in healthy volunteers.
Main Methods:
- Whole blood samples from 15 healthy volunteers were collected at 0800, 0830, 1200, and 1700 hrs.
- Platelet function was assessed using the PFA-100 method with collagen and ADP or epinephrine.
- Results were measured as closure time (seconds), with longer times indicating reduced platelet aggregation.
Main Results:
- Platelet closure time increased throughout the day for both ADP and epinephrine agonists.
- The increase was statistically significant for ADP (p=0.03) and highly significant for epinephrine (p=0.002).
- A non-significant trend for decreased closure time was observed upon rising.
Conclusions:
- A diurnal rhythm in platelet function exists when assessed using whole blood at high shear rates.
- These findings are more relevant to in vivo conditions compared to previous optical aggregometry studies.
- The diurnal variation in platelet function may contribute to the morning peak in myocardial infarction.