EVALUATION OF A METHOD TO ASSESS PLASMA VISCOSITY - THE FALLING BALL VISCOMETER

Several methods are presently used to evaluate plasma viscosity and it s variation. The falling ball viscometer, in spite of its cheap runnin g cost, has been only used by a limited number of laboratories. We wis h in this article to give our own appraisal of the technique. We studi ed the influence of the individual glass syringes and stainless steel balls, as well as the temperature dependence on plasma viscosity value . Freezing plasma samples did not appear to affect the value of plasma viscosity, as well as the mode and frequency of thawing, since the va riations (0.01 mPa.s or less) were equivalent to the reliance of the t echnique (0.01 mPa.s, 1%). A reference range for healthy controls was determined. We could not detect any significant difference between men and women for plasma viscosity values. In spite of the fibrinogen inc rease with aging or smoking, we could not observe any significant vari ation for plasma viscosity values in healthy controls. However, in a l arge range of fibrinogen values, a good correlation was found between plasma viscosity and fibrinogen concentration (r2 = 0.460; p = 0.0001) . In 9 patients with IgG myeloma, a significant correlation between se rum viscosity and IgG concentration was obtained (r2 = 0.797; p = 0.00 1). Concomittant measurements of plasma viscosity with a rotational vi scometer (Contraves LS30) showed a strong correlation with our values (r2 = 0.980). We conclude that falling ball viscometry is a valid tech nique to measure plasma viscosity variations in clinical or research s tudies.