The effects of time interval after venipuncture and of anticoagulation on platelet adhesion and aggregation.

Abnormal platelet function plays an important role in atherosclerosis and thrombotic disorders. Simple in vitro testing of platelet function is preferable to other techniques, and adhesion measurement is especially important because it reflects an immediate platelet response. The time lapse after venipuncture and the anticoagulant may affect platelet function in an as yet unknown way. A method for determining platelet adhesion under controlled whole blood flow conditions and an aggregation study were used. Platelet adhesion and aggregation changed significantly with time elapsed since venipuncture, peaking after 60 min (P < 0.05): a plateau was reached only after more than 120 min. Platelet adhesion was directly suppressed by the use of sodium citrate as an anticoagulant, and surface density decreased from 14.2 to 8.8 (P < 0.001). To prevent the effect of time after venipuncture on platelet function, testing should be performed at the plateau phase.