Comparison of cation-osmotic haemolysis in normal and low birth weight newborns during the first month of life.

The present study was designed to compare cation-osmotic haemolysis (COH) in normal versus low birth weight newborns during the first month of postnatal life. COH was assessed in 80 normal (NBW) and 45 low birth weight newborns (LBW). A significant decrease in COH in the solutions with low ionic strength (15.4-30.8 mmol.l-1 NaCl) was found in LBW in the early period after birth when compared with NBW (p<0.01; p<0.001). In the solutions with high ionic strength (123.2-154.0 mmol.l-1 NaCl), COH again was significantly lower in LBW than in NBW neonates (p<0.01; p<0.001). The differences in COH were still present after both two weeks and one month of postnatal life but only in the solutions with the highest ionic strength (138.6-154.0 mmol.l-1 NaCl) (p<0.01; p<0.001). To conclude, our study demonstrates that COH is significantly lower in LBW than in NBW neonates. Furthermore, the latter show still lower values than adults. Finally, the relationship between COH and erythrocyte deformability is discussed.