Rheological blood behaviour is not related to gender in morbidly obese subjects.

To the Editor. We have read with interest the recently published article by Wiewióra et al. [7] regarding hemorheological differences related to gender in morbidly obese subjects. In this study authors found several hemorheological differences between male and female. In this sense, males showed higher blood viscosity and higher erythrocyte deformability than females and native blood viscosity correlated with several erythrocyte aggregation parameters evaluated with the Laser-Assisted Optical Rotational Cell Analyser (LORCA) [3]. In studies with small sample sizes (18 men and 20 women) there is always the risk that differences in certain variables may appear by chance or by imbalances in the groups. Moreover, it was not discussed why the erythrocyte deformability should be higher in males. Therefore we aimed to evaluate the rheological profile in a larger sample of morbidly obese subjects selected for bariatric surgery, to ascertain whether there are rheological differences in morbidly obese related to gender. Before statistical testing, all continuous variables were checked for normal distribution. Those who were markedly skewed, were log transformed to improve normality. Analytical tests were performed according to previous studies of our group [4, 5] and in accordance with the ethical guidelines for Clinical Hemorheology and Microcirculation [1]. Results are expressed in Tables 1 and 2 as mean ± sd. P values <0.05 were considered as statistically significant. All analyses were performed using the Statistical Package of Social Sciences (SPSS, version 11.0) for Windows. The results of the present study revealed no differences in erythrocyte deformability, at any of the shear stresses tested when males and females were compared, in line with the homogeneity of erythrocyte indices in both groups. In this sense, Wiewióra’s study did not include any information on erythrocyte indices [7], although these indices are of paramount importance when evaluating erythrocyte deformability [2, 6].