MEASUREMENT OF PLASMA VISCOSITY - COMPARISON OF FOUR VISCOMETERS

For more then two decades, only the Harkness-Coulter viscometer was commercially available in routine clinical plasma viscosity testing. Three new clinical viscometers (manufacturers: Haake, FRG; Luckham, UK; Rheomed, FRG) have been compared to the Harkness viscometer in an extensive quality control program. Sample-to-sample, day-to-day and long term variations have been studied and compared, furthermore error sources, health and environmental hazards, sample volume, price, running costs and user friendliness have been evaluated. Among the four machines tested, the Luckham viscometer appeared to be the most versatile, especially because of its reliability and user friendliness. The smallest sample volume (10 times less than any of the others) is required by the Haake falling ball microviscometer. It provides repeated tests from a sample volume less than 0.1 ml, at comparable price, and with still acceptable accuracy. The exactness of the Rheomed machine is jeopardized by the varying diameter of disposable plastic capillary tubing used in this method.