Flow cytometric analyses of PS-positive platelets in whole blood from a representative patient with SCD.

Dot plots of forward size scatter verses anti-CD61–PE fluorescence from a blood sample stained in the presence of EDTA and calcium are presented in panels A and B, respectively. Region R1 in these dot plots represents platelet-associated events. Histogram profiles of annexin V–FITC fluorescence of platelets stained in the presence of EDTA and calcium are presented in panels C and D, respectively. Annexin V–negative (gate M1) and –positive (gate M2) histogram regions were set by using the blood sample stained in the presence of EDTA as shown in panel C. The histogram profile presented in panel D demonstrates the presence of a subpopulation of PS-positive platelets (gate M2).