Mean platelet volume: the need for a reference method.

The time course of artifactual effects due to anticoagulants, specimen temperature, and interval between venipuncture and analysis on platelet volume measurements was evaluated. Split specimens were analyzed using hydrodynamic focusing, and platelet distributions were computed using a least-squares fit to a log-normal distribution. Significant artifacts resulted from exposure to EDTA, cooling to room temperature, and delay in exposure to anticoagulant. The artifactual effect of EDTA is extreme and time dependent. Collection of blood in Buffered Citrate, Acid Citrate Dextrose, or Pyridoxal-5'-phosphate supplemented Citrate yielded stable and equivalent results with rapid anticoagulation and incubation at 37 degrees C for up to six hours.