Plasma Viscosity ( PV )

Haematology

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Description

Plasma Viscosity (PV) estimation is a non-specific test reflecting changes in plasma proteins. Values from normal subjects are within a narrowly defined range and are unaffected by physiological stimuli. The major influence on Plasma Viscosity is exerted by fibrinogen and immunoglobulins. Fibrinogen responds as an acute phase reactant and is raised in the initial stages of any inflammatory response. In infection the initial response is followed by an increase in immunoglobulin which will maintain a high plasma viscosity. In autoimmune conditions e.g. rheumatoid disease, the increased immunoglobulins, along with the inflammatory response, produce a raised plasma viscosity. Conditions that secrete paraproteins e.g Myeloma or Macroglobulinaemia are associated with a very high PV. Untreated myeloma frequently has PV values of >3mPa while plasma containing macroglobulins can have values greater than 10mPa

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Indications

1. Acute Phase Response

When the human body is subjected to physiological stress it prepares itself to fight or flee. Injury to the body can lead to blood loss and infection, therefore the body prepares itself by increasing the circulating levels of proteins to combat these insults. To prevent blood loss fibrinogen levels are increased and to combat infection immunoglobulin levels rise. The rise in concentration of these 2 proteins produces a reciprocal rise in plasma viscosity over the resting state. This reaction is called the acute phase response and occurs within 2-24 hours of the insult.

2. Rheumatoid Disease

The plasma viscosity cannot diagnose any rheumatoid disease, but when taken in conjunction with a clinical assessment, a result in the range of 1.75-2.00 mPa�s can give a good indication of an underlying problem. Where the plasma viscosity comes into its own is in the monitoring of patients with these conditions. Steroids are frequently administered to control the severity of the symptoms. Other laboratory tests (ESR) can (with high dose steroid therapy) revert to normal even when the underlying condition is not improving. Plasma viscosity results follow the severity of the condition with serial higher results showing deterioration or lower results indicating improvement.

3. Malignant Disease

Non-invasive or primary neoplasia can be associated with a normal plasma viscosity. Once secondary sites occur, or when the malignancy becomes invasive there is usually a moderate rise in the plasma viscosity. A patient with a raised plasma viscosity, with no known cause, should be investigated for an underlying neoplasia

4. Paraproteinaemias

This group of disorders are associated with markedly raised plasma viscosities and the complication of hyperviscosity syndrome. The degree of hyperviscosity is related to the immunoglobulin sub class excreted by the malignant cells, IgG paraproteins commonly having viscosities of around 3mPa�s; while IgA and more especially IgM paraproteins can give values of 10-20mPa�s. In most cases of hyperviscosity syndrome the symptoms can be rapidly relieved by performing therapeutic plasma exchange. As the plasma viscosity is the only test, which can directly measure viscosity, it is recommended that patients with these conditions should have serial tests.

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Sample Type

Plasma (EDTA 4.0ml Lavender) - up to 1 week old. DO NOT REFRIGERATE.

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Reference Range

1.50-1.72 mPa

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Turnaround Time

Within 1 day

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Testing Frequency

Daily

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.