Acute effect of a high-carbohydrate low-fat meal on platelet aggregation.

Conflicting information is available regarding patient preparation with respect to the fasting and feeding states prior to blood collection in order to conduct platelet aggregation tests. Some literature suggests avoidance of only high-fat foods and allowance of non-fat foods and clear liquids; others suggest a fast of 8-10 hours. We conducted a study in 16 healthy subjects aged 44.0 +/- 12.7 (mean +/- SD) years to investigate and compare the effects of fasting and a high-carbohydrate low-fat meal on measures of platelet aggregation. Blood samples collected after an overnight fast of 10-12 hours and those collected at 40 and 120 minute postprandially (post-high-carbohydrate low-fat meal; 1900 kJ energy; 69, 16 and 15% of energy from carbohydrate, protein and fat, respectively), were tested for platelet aggregation in response to adenosine diphosphate. There was a significant reduction in maximum aggregation and area under the aggregation curve from fasting to 120 minute post meal (overall p < 0.001). Serum triglyceride concentrations did not change significantly from fasting to postprandial state (p = 0.53). Although there was a significant association between serum insulin, plasma glucose and measures of platelet aggregation, correcting for the effects of these metabolic parameters did not alter the results, providing evidence that other, currently unknown, factors associated with food consumption affect postprandial platelet aggregation. We propose that protocols for control of pre-analytical variables in platelet aggregation studies should make a fasting sample mandatory rather than "preferable" unless the objective of the study is to measure acute effects in response to a medication or food.