Do you account for the effect of coffee on platelet aggregation studies?

Although recommendations from the International Society of Thrombosis and Haemostasis (ISTH) [1] suggest that individuals should avoid caffeine for at least 2 hours before blood is drawn for light transmission platelet aggregation studies, (and be fasting, be rested for 30 minutes, and avoid smoking for at least 30 minutes), there is controversy about these recommendations. A careful study showed that these measures do reduce intra-individual variation [2]; however, when these variables were studied again in normal subjects, there were no significant changes between normal subjects in platelet aggregation using the variables [3].

I believe it is reasonable to apply the ISTH recommendations to patients whenever it is possible, but when it is ...