Plasma viscosity

Most UK laboratories print 1.50 to 1.72 mPa.s at 25 degrees; unlike the ESR it is not affected by age, sex or anaemia, though it is a little higher in pregnancy.

Plasma viscosity measures how thick, or sticky, the fluid part of the blood is once the cells have been removed. The thickness is set by the proteins dissolved in the plasma, and those proteins rise with inflammation and with some blood disorders. It is used in some parts of the UK in place of the ESR because it does not depend on the red cells.

Doctors request it, often alongside CRP, when looking for inflammation, particularly in older people with aches, headaches or unexplained symptoms, and when looking at abnormal blood proteins. Which of ESR and plasma viscosity a laboratory offers is mainly regional habit.

• Infection and inflammatory conditions such as rheumatoid arthritis, polymyalgia and vasculitis
• High blood protein levels, including myeloma and related conditions
• Some cancers
• Pregnancy, a little
• Being overweight, a little

• Settling of the inflammation that raised it, over days to weeks
• Low blood protein, as in poor nutrition, liver disease or protein loss through the kidneys
• Treatment with immune-suppressing medicines

• A recent infection or vaccination raises it for a week or two
• A large protein-rich meal shortly before the test has a small effect
• Methods differ slightly between laboratories

No fasting needed. It responds more slowly than CRP, so the trend over repeated tests is more useful than one value. It is a stable test and does not need to be processed quickly.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.