Plasma Viscosity

Plasma Viscosity: The Key To definitive clinical diagnosis

Plasma viscosity is a quick, simple, inexpensive, non-specific test, useful as a broad screening test and for condition monitoring. However, it is capable of being a more definitive diagnostic tool for specific conditions. Plasma viscosity will provide practical information for the diagnosis and treatment of many diverse clinical disorders:

  • Multiple Myeloma
  • Waldenström’s Macroglobulinaemia
  • Cardiovascular Diseases
  • Respiratory Diseases v Sickle Disease
  • Diabetes
  • Rheumatoid Arthritis
  • Polymyalgia Rheumatica
  • Temporal Arteritis
  • Sepsis
  • Meningitis
  • COVID-19.

Clinical viscosity test results are repeatable, reproducible, and reliable, diagnosing complex infectious and inflammatory conditions that pose significant challenges. Especially when timely diagnosis is crucial as with Sepsis, Meningitis and Temporal Arteritis.

The viscosity of plasma is determined by the concentration of proteins in the blood which usually increase as part of the body’s normal response to infection, inflammation, and due to the effects of traumatic injury. The viscosity of plasma is also determined by the concentration of the large asymmetric molecules such as fibrinogen. The plasma viscosity test is the most sensitive and reliable measure to detect minor changes in the acute phase protein reactants. Moreover, it proves to be significantly superior at monitoring clinical prognosis.

Any minor changes are significant for any individual 0.05 mPa.s or more. Testing can be performed on a sample up to seven days old. The test only aspirates 50µl of patient, sample one and a half drops so repeat paediatric tests can be achieved.

The plasma viscosity test can use the residue of a Full Blood Count test tube, eliminating the need for additional blood sample tubes.

Plasma viscosity really has got much more to offer than C-reactive protein (CRP) and Erythrocyte Sedimentation Rate (ESR). The plasma viscosity test can diagnose and monitor any condition that the ESR test is used to screen or monitor. However, it is important to note that all the plasma viscosity test results cannot always be substituted by CRP or ESR.

the Clinical and technical aspects of pV and ESR compared

Plasma Viscosity

ESR

Normal range same for both sexes.Normal range is different between the sexes.
Unaffected by physiological stimuli except in pregnancy and children under 3 years of age.Influenced by age, gender, alcohol consumption, smoking, physical activity, and metabolic abnormalities.
Increased result due to the change in protein concentration mainly fibrinogen and/or globulins.No exact cause can be stated for ESR increase. Due to Red cell shape rigidity and concentration.
Abnormal results will be detected earlier.Abnormal results are detected later.
Very low incidence of false negative results.High incidence of false negative results.
Serial monitoring tests on a patient will indicate any small change in condition presented on a plasma viscosity trend graph.ESR results show irregular peaks and troughs without clinical explanation.
High dose steroids do not interfere and affect the test results.High dose steroids may return ESR to normal Underlying disease may not be identified.
Salicylates (aspirin) have no effect on plasma viscosity results.Salicylates can lower the ESR result misrepresenting the true patents condition.
Polycythaemia does not interfere with plasma viscosity measurement results.Polycythaemia can produce a normal ESR irrespective of the underlying disease.
Myeloma and Macroglobulinaemia are characteristic and can be diagnostic.ESR cannot distinguish between protein abnormalities and inflammatory conditions.
Unaffected by time-induced deterioration and can be analysed up to 1 week post sampling.Must be analysed within 4 hours of sampling. EDTA anticoagulant sample. Westergren method.
PV is not affected by anaemia.Is affected by anaemia result will tend towards normal.
Variations in red cell size and shape have no effect.Red cell size and shape, variations, rigidity, and aggregation affect the rate of sedimentation.
All results are universally comparable because of calibration using fully traceable reagents.Results not universally comparable. Different anticoagulants, tubes, and timing methods.

Independent External Quality Assessment service clinical laboratories worldwide. UK NEQAS

No Independent Quality Control possible.

Time from receipt of sample and centrifugation. Testing can take less than 4 minutes.

Time factor from receipt of sample, setting up and reading of result can take 60 minutes if the correct Westergren principle is followed.

The SI. System International units of dynamic clinical viscosity are millipascal-seconds. 1 mPa.s is equivalent to 1 cP. Centipoise. Named after Jean Poiseuille Centimetre-gram-second CGS.

Interpretation of PV Results

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