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Detection of increased viscosity
Monitoring patients with hyperviscosity syndrome
Viscosity is the property of fluids to resist flow. Hyperviscosity may be manifested by oronasal bleeding, blurred vision, headaches, dizziness, nystagmus, deafness, diplopia, ataxia, paresthesias, or congestive heart failure. Funduscopic examination reveals dilation of retinal veins and flame shaped retinal hemorrhages.
The most common cause of serum hyperviscosity is the presence of large concentrations of IgM monoclonal proteins, and Waldenstrom's macroglobulinemia accounts for 80% to 90% of hyperviscosity cases. Hyperviscosity syndrome can also occur in multiple myeloma patients.
Because the ability of a monoclonal protein to cause hyperviscosity is affected by its concentration, molecular weight, and aggregation, sera with concentrations of monoclonal IgM >4 g/dL, IgA >5 g/dL, or IgG >6 g/dL should be tested for hyperviscosity.
Serum viscosity and electrophoresis are recommended before and after plasmapheresis in order to correlate viscosity and M-spike with patient symptoms. This correlation may be useful for anticipating the need for repeat plasmapheresis.
> or =16 years: < or =1.5 centipoises
Reference values have not been established for patients that are <16 years of age.
Although viscosities >1.5 centipoises (cP) are abnormal, hyperviscosity is rarely present unless the viscosity is >3 cP.
This test is not suggested in patients with small concentrations of monoclonal proteins.
Hyperviscosity syndrome may not be present even if the viscosity is >3 centipoises.
Gertz MA, Kyle RA: Hyperviscosity syndrome. J Intensive Care Med. 1995;10:128-141