Morphological assessment of platelet activation in thalassemia.

Platelets from patients with beta-thalassemia/hemoglobin E, both splenectomized and nonsplenectomized cases, were examined in comparison to those from normal subjects by scanning electron microscopy. In normal subjects, the majority of platelets were discoid (mean +/- SD, 81.0 +/- 3.9%) with 17.3 +/- 3.5% type I spherical shapes (platelet with long axis/short axis greater than 1.1) and 1.3 +/- 1.0% type II (long axis/short axis = 1.0-1.1). The thalassemic patients had significant lower percentage of discoid platelets (60.9 +/- 8.1% in nonsplenectomized patients, 49.2 +/- 9.1% in splenectomized patients) and increase in spherical platelets (nonsplenectomized patients had 36.6 +/- 8.3% type I, 4.0 +/- 1.5% type II; splenectomized patients had 43.4 +/- 7.9% type I, 8.3 +/- 4.5% type II). Study of platelet reversibility from pseudopods to smooth surface showed that thalassemic platelets had poorer reversibility than normal platelets. Splenectomized patients had lower platelet pseudopod reversibility than nonsplenectomized cases. The shape changes and impaired reversibility of platelet pseudopods may be associated with the high tendency of pulmonary thrombus in beta-thal/HbE patients.