Plasma Viscosity

Department of Haematology

Notes

The Plasma Viscosity, alongside the ESR and C-Reactive Protein tests, gives a measure of the acute phase response; i.e. the increase in assorted plasma proteins and fibrinogen in blood plasma stimulated by a variety of causes (e.g. infection, neoplasm or inflammatory disease). The value of these tests is limited by lack of specificity. Their main use is as an objective guide to the underlying activity of certain chronic inflammatory diseases such as temporal arteritis or rheumatoid arthritis.

Plasma Viscosity tests are performed at GRH.

Plasma Viscosity v ESR

Plasma viscosity and ESR results give very similar information. At GHNSHFT the plasma viscosity is used more routinely, and clinicians are advised to use this test in preference to the ESR as the plasma viscosity:

• becomes abnormal earlier in disease
• has a lower instance of false normal values
• is not affected by haematocrit
• can be performed on a sample up to 48 hours old
• is stable and relatively small changes are significant for any individual
• is technically reproducible and standardised
• is automatable and therefore safer and cheaper to perform

Plasma Viscosity v CRP

C-Reactive Protein is an acute phase reactant. Compared with plasma viscosity it is elevated earlier in infection (6 - 10 hours) and it has a shorter half life (48 hours). It tends not to be elevated in viral infections, leukaemia/lymphoma or connective tissue disease. It therefore has specific value as an early pointer to bacterial infection where the diagnosis may be difficult (e.g. children, in the presence of active connective tissue disease or in patients with lymphoma/leukaemia) and subsequently to monitor response to antibiotics.

CRP samples are analysed in the Chemical Pathology department

Sample Requirements

2ml or 4ml EDTA sample

Turnaround Times

Four days

Sample Storage and Retention

• Pre analysis storage: do not store, send to laboratory within 4 hours.
• Sample retention by lab: EDTA samples are retained for a minimum of 48 hours.

This test can be added on to a previous request as long as there is sufficient sample remaining and the sample is less than 48 hours old.

Reference Ranges