FLT1 and endothelial dysfunction: Moreover, one clinical study of 130 patients with CKD stage 3a to 5 and 56 controls in Germany also reported higher plasma soluble Flt-1 in CKD patients and significant association of the soluble Flt-1 level with decreased estimated glomerular filtration rate (GFR) as well as increased plasma von Willebrand factor, a marker for endothelial dysfunction [21].