Cryohemolysis, erythrocyte osmotic fragility, and supplementary hematimetric indices in the diagnosis of hereditary spherocytosis

Background Hereditary spherocytosis (HS) is a chronic hemolytic anemia characterized by micro-spherocytes in the peripheral blood and increased erythrocyte osmotic fragility (EOF). This study evaluated the cryohemolysis test (CHT); initial hemolysis (IH); immediate and incubated hemolysis percentage in 5.5 g/L NaCl (H5.5); mean corpuscular hemoglobin concentration (MCHC); red blood cell distribution width (RDW); and Hb/MCHC, Hb/RDW, and MCHC/RDW ratios for the diagnosis of HS. Methods Data from 13 patients with HS were evaluated at the Instituto de Bioquimica Aplicada and compared with data from 14 unaffected individuals and 11 patients with anemia due to another etiology. Total blood and reticulocyte counts, CHT, and immediate and incubated EOF were performed in all subjects; sensitivity, specificity, efficiency, and Youden index (YI) were calculated. Results Eight patients with HS had MCHC >= 345 g/L, 10 had RDW >= 14.5%, 12 had IH > 5.0 g/L, 11 had immediate H5.5 >= 5%, and 13 had incubated H5.5 >= 50% (the cut-off value to consider HS). The efficiency and YI were: immediate H5.5 (0.94-0.85), incubated H5.5 (0.89-0.82), IH (0.89-0.78), MCHC (0.87-0.62), CHT (0.84-0.54), and Hb/MCHC (0.71-0.56), respectively. The calculated ratios could distinguish subjects with HS from unaffected individuals (P<0.05), but not those with anemia of another etiology (P>0.05). Conclusion Although the CHT and supplementary hematimetric indexes were useful to differentiate individuals with SH from healthy controls, they cannot distinguish from anemias of other etiology. CHT and MCHC, in addition to EOF, are recommended for diagnosing HS patients because of their low cost and efficiency.