The GEN.S: a fortuitous finding of a routine screening test for hereditaryspherocytosis

As part of the evaluation of the GEN.S (Coulter(R)), we compared the Mean C orpuscular Volume (MCV) to the Mean Spherized Corpuscular Volume (MSCV) ass essed during the reticulocyte count procedure under hypo-osmotic conditions . A sub-group of patients with hereditary spherocytosis (HS) was singled ou t: in all of them, the MSCV became smaller than the MCV. As the cell volume normally increases in red cells derived from other patients in the same co nditions, we decided to further study the reason for this particular behavi our of HS red cells. Whereas normal red cells are able to undergo an osmoti c expansion, the spherocytes reach a critical osmotic volume leading to cel l fragmentation consistent with the decrease of MSCV. This fortuitous findi ng is likely to be a reliable improvement for the routine screening of HS.