Viscosity refers to the property of fluids that enables them to resist flow. Measuring the viscosity of serum, plasma, or whole blood can be valuable in diagnosing and monitoring patients with hyperviscosity syndromes, which are often associated with conditions like multiple myeloma and Waldenstrom's macroglobulinemia. These measurements are reported as a relative viscosity compared to water, where normal serum and plasma have a relative viscosity of up to 1.6. While values greater than 1.6 are considered abnormal, hyperviscosity syndromes typically do not manifest unless the relative viscosity reaches approximately 4.0 or higher.
The most common cause of serum hyperviscosity is the presence of high concentrations of IgM monoclonal proteins. Waldenstrom's macroglobulinemia is responsible for 80% to 90% of symptomatic hyperviscosity cases. Hyperviscosity syndrome can also be observed in patients with multiple myeloma, and, in rare instances, it may occur in patients with high levels of rheumatoid factors and other proteins that tend to aggregate.
Viscosity, Serum
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