  This study proposes a novel stochastic model for the study of hyposmotic
hemolysis. This model is capable of reproducing both the kinetics in the
transient phase and the lysis equilibrium in the stationary phase, as well as
the variability of the experimental measurements. The stationary distribution
of this model can be approximated to a normal distribution, with mean and
variance related to the salt concentration used in the erythrocyte osmotic
fragility assay. The proposed model can generalize the classical Boltzmann
sigmoidal model often used in adjusting the stationary experimental data
distribution. A typical osmotic fragility curve is constructed from the
absorbance of free hemoglobin as a function of the decrease in NaCl (X)
concentration and allows the determination of H50, an osmotic fragility
variable that represents the saline concentration capable of promoting 50%
lysis, and dX, an osmotic stability variable that represents 1/4 of the
variation in salt concentration required to promote 100% lysis. Based on the
stationary distribution of the proposed model it is possible to stratify a
population into different groups of individuals with similar levels of cell
stability. These groups are very suitable to study the factors associated with
cell stability, such as gender, age and lipids, among others. The method
presented here was applied to a sample of 71 individuals and several results
were obtained. In a group of 25 female subjects, with H50 values between 0.42
and 0.47 g/dL NaCl, for example, the use of a quadratic model to study the
dependence of the stability index dX/H50 with blood LDL-cholesterol levels,
showed that the erythrocyte osmotic stability increases with increasing LDL-C
to a maximum value close to 90 mg/dL and then decreases.
