Haemostasis Alterations in Sickle Cell Disease.

Sickle cell disease (SCD) is considered by many workers to be a hypercoagulable state. The vaso-occlusion in sickle cell disease is complex, involving adhesive processes between sickle red blood cells, leukocytes, and the activated endothelium. Loss of normal membrane phospholipids asymetry with the appearance of phosphatidylserine on the erythrocyte surface has been documented as promoting an exacerbation of the anaemia and an activation of coagulation. The aim of this study was to monitor changes in coagulation and platelet activation (monitored by measuring the levels of procoagulant phospholipids microparticles - PPM) in SCD (both in steady state and crisis). Coagulation screening tests (PT, APPT), Protein S (PS), D-Dimer (D-Di) and PPM were measured in plasma samples obtained from 18 patients with SCD (8 in crisis state and 10 in steady state) and in twenty one normal volunteers as control. All blood samples were collected and the plasma prepared in the same hospital using the same conditions. All plasma samples were stored at -80°C until assayed. PT, aPTT, PS and D-dimers were measured using reagents from Diagnostica Stago, Asniéres, France. PPM was monitored with a novel factor Xa-based coagulation assay. In this assay shortened clotting times are associated with increased levels of PPM and thus platelet activation.

In sickle cell crisis a significant increase in both coagulation and platelet activation, as monitored by PPM, was found (all at p < 0.001). The decrease in % PT and PS levels confirms the findings of others. In steady state only DDi levels are significantly higher than controls. Further studies are needed to explain these findings. Although this was a small pilot study and further studies are needed it is interesting to speculate on the possible usefulness of the PPM assay in monitoring SCD crisis.