Figure 1.

Effect of CTAD matrix on platelet activation and TGFβ measurements. A) Markers of platelet activation. Both PF4 and BTG were substantially elevated in samples collected in EDTA tubes from normal donors, confirming that some level of ex vivo platelet activation occurs in EDTA plasma draws. (Open symbols represent values outside the range of the assay). B) Within-donor TGFβ levels in CTAD and EDTA tubes. EDTA TGFβ levels were higher than CTAD tube levels for all donors, ranging from 1.7- to 5.3-fold higher.

Abbreviations: BTG, beta-thromboglobulin; CTAD, citrate-theophylline-adenosine-dipyridamole; EDTA, ethylenediamine tetra-acetate; PF4, platelet factor 4; TGFβ, transforming growth factor beta.