Platelet distribution width: a simple, practical and specific marker of activation of coagulation.

BACKGROUND: Platelet indices are potentially useful markers for the early diagnosis of thromboembolic diseases. An increase in both mean platelet volume (MPV) and platelet distribution width (PDW) due to platelet activation, resulting from platelet swelling and pseudopodia formation was hypothesized. METHODS: Platelet indices (MPV and PDW) in three groups of persons, using impedance and optical technology were measured. The first group consisted of patients with established platelet activation and healthy control subjects. The second study group included pregnant women in different trimesters of pregnancy. The effect of storage time on MPV and PDW in blood samples of a third group of randomly chosen patients was also assessed. RESULTS: There was a significant increase in MPV (P<0.001) and PDW (P<0.001) in patients with confirmed platelet activation compared to healthy control subjects. Only PDW showed a significant increase from the first to the third trimester of pregnancy (P=0.009). Temporal changes of MPV and PDW over storage time revealed a significant increase in MPV (P<0.001), in contrast to a significant decrease in PDW (P<0.05). CONCLUSION: MPV and PDW are simple platelet indices, which increase during platelet activation. PDW is a more specific marker of platelet activation, since it does not increase during simple platelet swelling.