Flow-cytometric analysis of erythrocytes and reticulocytes in congenital dyserythropoietic anaemia type II (CDA II): value in differential diagnosis with hereditary spherocytosis

Congenital dyserythropoietic anaemia type II (CDA II) is the most common co ngenital dyserythropoietic anaemia. CDA II is frequently misdiagnosed as He reditary Spherocytosis (HS) due to the presence of mild chronic haemolytic anaemia with splenomegaly, increased osmotic fragility, and presence of mic rospherocytes. Accurate diagnosis of CDA II is important to prevent severe iron overload. Erythrocyte and reticulocyte indices were assessed in 10 patients from six families with CDA II, 18 patients from eight families with HS, and 50 norma l controls. Characteristic increases in distribution width were present in CDA II for cell volume (RDW, anisocytosis) and in HS for cell haemoglobin c oncentration (HDW, anisochromia), resulting in an RDW/HDW ratio which was s ignificantly greater in CDA than HS (P < 0.0002). A cut-off value for RDW/H DW of 5.34 resulted in 89% sensitivity and 70% specificity in distinguishin g CDA II from HS. Distribution width for cell haemoglobin content of reticu locytes (CHDWr) was characteristically increased in CDA II, resulting in a CHDW/CHDWr ratio significantly lower in CDA II than HS (P < 0.0002). A cut- off value of 0.98 provided 89% sensitivity and 80% specificity in distingui shing CDA II from HS. These differences in distribution widths of flow-cytometric parameters of r eticulocytes and mature erythrocytes reflect the different pathogeneses of the two diseases and are helpful for the differential diagnosis of these tw o conditions.