Comparison of blood viscosity using a torsional oscillation viscometer and a rheometer.

The absence of a simple and clinically practical method to determine whole blood viscosity can partly justify why the medical community has been slow in realizing the significance of whole blood viscosity. For this reason, the availability of a technique able to evaluate blood viscosity in a rapid and direct manner is welcome. To evaluate the feasibility in hemorheological laboratory of a new torsional oscillation viscometer, it was compared with a conventional cone-plate system. The viscosity comparison has been related to hematocrit value both on whole blood and suspended blood in a saline solution. The results showed a good repeatability and reproducibility of the new equipment, with a best-fitting data of the hematocrit 0-100% range characterized by coefficient of determinations, r2>0.95. Furthermore, a comparison of whole blood viscosity as measured by the two instruments was done on blood samples collected from hospitalized patients. Reasonable agreement for the viscosity values was found between the two methods with linear determination coefficients between the two measurement methods comprised between r2=0.7329 and 0.9263, depending on shear stress phase and the corresponding shear rate.