RESUMO
This article discusses the fundamentals for measuring the viscosity of whole blood, serum, and plasma and its application to the diagnosis of hyperviscosity syndrome. We describe some of the terminology in the field, including relevant definitions, the different units of measure, and general principles of clinical laboratory viscosity measurement. The 3 main categories of instrumentation for viscosity measurement--capillary, falling-sphere, and rotational viscometers--are discussed. We compare the various types of instrumentation for their usefulness with various types of clinical specimens. Relevant features that may be important in selecting a viscometer are described. We describe our 1.5-year experience with the viscometer that we chose. We hope the information in this review will be useful to pathologists and clinical laboratory staff in explaining the available choices for measuring serum, plasma, and whole blood viscosity.