La cytométrie en flux dans un laboratoire d'hémostase

Flow cytometry provides a new tool for laboratories specialized in haemostasis. Today, the method is used to investigate platelets. Indeed, membrane glycoprotein defects can be easily detected, allowing to screen some inherited platelet defects. Comparing to conventional aggrometry, the method is rapid and easy to handle, and requires a small sample volume (a few microliters of citrated whole blood), and this is a major advantage for children. Furthermore, the technique is not influenced by the optical density of the sample in non fasting babies. Flow cytometry allows to study platelet activation: in response to platelet agonists, the method can analyze the expression of GPIlbIlla, GPlb and P-selectin at the membrane surface. The conformational changes secondary to GPIlbIlla activation or ligand binding can be recognized using specific antibodies. Baseline platelet activation, or in vitro agonist-induced platelet activation, have been extensively studied in artery diseases, particularly to monitor anti-platelet dugs. Contrary to aggregometry, flow cytometry can distinguish the effect of each specific drug (i.e. anti-GPIlbIlla versus thienopyridins) in a multiple anti-platelet drug combination. Flow cytometry offers a full range of platelet investigations in the field of platelet immunology, diagnosis of heparin-induced thrombocytopenia, platelet turn-over, platelet signalling, miscellaneous platelet disorders (i.e., storage pool diseases…). Current and future applications are dependent on the availability of antibodies. A crucial point is standardisation, not only between laboratories, but also, within each laboratory, between instruments. Other points are, for each laboratory, to establish normal values, and to decide how to integrate flow cytometry in a decision tree for platelet assessment.