Serum Viscosity

Viscosity is the property of fluids to resist flow. The viscosity of water at 20 degrees Centigrade is 1.0 centipoise (cP). Centipoise units are named after Jean Leonard Marie Poiseuille, a French physicist. Serum viscosity can be directly measured and compared to the viscosity of water. The viscosity of serum from a healthy person is less than 1.5 cP. 

Hyperviscosity may cause epistaxis, headaches, nystagmus, deafness, blurred vision, diplopia, paresthesia, or congestive heart failure. Clinical hyperviscosity is rarely present unless viscosity is greater than 3 cP. 

The most common cause of hyperviscosity is Waldenstrom macroglobulinemia which produces high concentrations of IgM monoclonal proteins. Hyperviscosity can also occur in patients with multiple myeloma with high concentrations of IgA or IgG monoclonal proteins. Viscosity should be measured in patients with an IgM concentration > 4g/dL, IgA >5 g/dL, and IgG >6 g/dL.

Measurement of serum viscosity is helpful in determining the need for plasmapheresis. Correlation of serum viscosity with the paraprotein level measured by serum electrophoresis is useful in anticipating the need for repeat plasmapheresis.

Viscosity is measured with an automated viscometer that uses vacuum pressure to draw serum through a capillary.

Reference value is 1.5 centipoises or less. Specimen requirement is a 3 mL red-top tube of blood.

References

Gertz MA, Acute hyperviscosity: syndromes and management. Blood. 2018; 132:1379-85.

Késmárky G, Kenyeres P, Rábai M, Tóth K. Plasma viscosity: a forgotten variable. Clin Hemorheol Microcirc. 2008;39(1-4):243-246.

Maqbool MG, et al, A practical guide to laboratory investigations at diagnosis and follow up in Waldenström macroglobulinaemia: recommendations from the Medical and Scientific Advisory Group, Myeloma Australia, the Pathology Sub-committee of the Lymphoma and Related Diseases Registry and the Australasian Association of Clinical Biochemists Monoclonal Gammopathy Working Group. Pathology. 2020;52(2):167-178.