Tissue factor-positive monocytes expression in children with sickle cell disease: clinical implication and relation to inflammatory and coagulation markers.

Hemostatic abnormalities are well documented in sickle cell disease (SCD). Nevertheless, whether these perturbations could contribute to sickle vasculopathy is still not clear. We evaluated monocytes tissue factor (TF) expression in children with SCD correlating the results with the clinical state and some inflammatory and coagulation markers. The study included 24 children with SCD in steady state, 24 in painful crisis and 20 healthy age and sex-matched children as controls. Complete blood count, prothrombin time (%), activated partial thromboplastin time, fibrinogen, D-dimer, thrombin-antithrombin complex and quantitative C-reactive protein were assayed. TF expression on monocytes was analyzed by flow cytometry. TF-positive monocytes were significantly higher in both patient groups compared with the controls, being higher in painful crisis group (2.06 ± 0.64, 8.01 ± 1.53, 13.5 ± 4.3 for the controls, steady state and painful crisis groups, respectively). Among painful crisis group, TF expression on monocytes was positively correlated with the pain rate, reticulocytes (%) and three out of six markers of inflammation and coagulation (C-reactive protein, D-dimer and fibrinogen) with inverse correlation with hemoglobin and the red blood cells count. TF-positive monocytes were more expressed in SCD both in steady state and in painful crisis, being significantly higher in painful crisis. This expression was significantly related to the pain rate as well as to markers of hemolysis, inflammation and coagulation among patients in painful crisis. These results confirm the substantial role played by TF-positive monocytes in the pathogenesis of SCD painful crisis.