Benson Viscometers Ltd
SAMPLE LETTER
2012
NHS Letter Head
Hospital Address
Tel:
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Email:
Date
FAO Practice Medical Staff
Dear Colleagues
The Haematology Department is upgrading its service. This includes changing one of its
tests frequently requested by general practitioners.
ESR will be replaced by the Plasma Viscosity test (PV). PV analysis removes some of the
non-clinical variables associated with the ESR and therefore gives an improved result for
diagnosis and monitoring of patients with chronic inflammatory disease. PV analysis is
undertaken from the routine EDTA (purple top) full blood count tube, so no new or
additional tube is required.
With the exception of clinical trials or specific patient testing, the laboratory will cease to
use ESR tests from (date).
Apart from small stocks, any outstanding ESR tubes should be returned to the laboratory.
Enclosed are some general guidelines on the clinical use of PV along with a comparison to
ESR results in detecting and monitoring chronic disease.
If having read the document you have any specific questions; please contact me directly
on the above telephone number or by e-mail.
Yours sincerely
.
Enc:
Benson Viscometers Ltd
SAMPLE LETTER
2012
PROPOSAL TO REPLACE ESR WITH PLASMA VISCOSITY
Background
Both plasma viscosity and ESR are used to monitor the acute phase response to “screen” for the
presence of infection or inflammation and to monitor “disease activity” but there are significant
differences between each test.
The Haematology Laboratory has reviewed its repertoire of tests and proposes to replace ESR
measurements with measurements of plasma viscosity (PV). The case for change, both from a
clinical and technical aspect, is made below.
Sample Requirements
A standard FBC sample (EDTA) is required for PV measurement. FBC and PV can be carried out
on the same sample; no additional sample is required. PV is stable at room temperature for up to 1
week post sampling.
Interpretation of Results
PV range
(mPa.s.)
PV range
(mPa.s.)
25ºC
37ºC
Normal
Range
1.40-1.75
1.05 - 1.30
Low
Results
< 1.40
< 1.05
Found in infants under 3 years old and patients
with low immunoglobulin or fibrinogen levels.
High
Results
1.75 - 2.00
1.30 - 1.46
Chronic disorders e.g. infection, malignancy,
vascular disease. Autoimmune such as rheumatic
diseases.
Very High
Results
2.01 - 3.00
1.47 - 2.18
Suggestive of myeloma. IgG-paraproteins. High
concentration of asymmetric paraproteins
Extremely
High
Results
>3.00
> 2.18
Suggestive of Waldenstrom's
macroglobulinaemia.
Grossly raised IgM-paraproteins.
Comments
Physiological Factors Influencing Plasma Viscosity
Age (after 3 years), gender, and diurnal rhythms have no effect on PV. Throughout life serial PV
measurements in a healthy individual vary as little as 0.05 mPa.s. The only physiological factor that
has a significant and consistent effect on PV is pregnancy. PV remains normal in the first two
trimesters and gradually rises to around 1.80 mPa.s in the final trimester.
Small variations in PV may be clinically significant.
Benson Viscometers Ltd
SAMPLE LETTER
2012
Plasma Viscosity in Disease

Acute phase response
As a result of the acute phase response many plasma proteins including fibrinogen and
immunoglobulins are increased and this is reflected in a rise in PV. This response occurs
within 2-24 hours.

Chronic inflammatory diseases
Like the ESR, PV cannot diagnose any condition. However, 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. ESRs and PVs are affected by different factors and are not
always equivalent (see Tables). Studies have shown PV to be equal or superior to the ESR
in monitoring of patients with rheumatoid arthritis and in the diagnosis of temporal arteritis.
While anaemia and the age of the sample can affect the ESR with no change in the
underlying condition, serial PV assessments will quite accurately reflect the progress of the
condition as they are not influenced by these factors.

Malignant disease
Early stage malignancy can be associated with a normal PV. With more advanced disease
there is often a moderate rise in PV.

Paraproteinaemias
This group of disorders can be associated with markedly raised PVs and such patients may
display symptoms of hyperviscosity (confusion, visual disturbance, epistaxis, difficulty
breathing, renal impairment). In general, IgM paraproteins are associated with much higher
PVs than IgG and IgA paraproteins, but this cannot be assumed or inferred because some
IgG and IgA molecules polymerize and lead to very high PVs.
NB: a normal PV, just the same as a normal ESR, does not exclude a diagnosis of light
chain only or non-secretary myeloma.

Severely ill patients
In severely ill patients (e.g. in intensive care) impaired synthesis and/or increased
degradation of plasma proteins may lead to a fall in PV. This should not be taken as an
indication of an improvement in the patient’s underlying condition in this situation.
Benson Viscometers Ltd
SAMPLE LETTER
2012
Comparison of PV and ESR: clinical aspects
Plasma viscosity
ESR
Normal range the same for both sexes
Normal range different for both sexes
Unaffected by physiological stimuli
(except in pregnancy)
Influenced by age and haematocrit
(Red cell concentration)
Increased result due to change in protein
concentration
(mainly fibrinogen and/or globulins)
No exact cause can be stated for increase in
ESR
(Changes in Red cell shape/concentration and
protein changes)
Abnormal results detected earlier
Abnormal results detected later
Low incidence of false negative results
High incidence of false negative results
Serial tests in an individual responding to therapy
would show a fall in PV on a continuous curve
ESR results show irregular peaks and troughs
without clinical explanation
High dose steroids do not normalise the PV.
(Inflammation must be reduced)
High dose steroids will return ESR to normal.
(Underlying disease may not be improved)
Salicylates have no effect on PV
Salicylates can lower the ESR result without
improving the underlying condition of the patient
Polycythaemia does not interfere with
measurements
Haematocrit >50% will produce a normal ESR
irrespective of the underlying disease
Results in myeloma and macroglobulinaemia are
characteristic and can be diagnostic
ESR cannot distinguish between protein
abnormalities and inflammatory conditions
Comparison of PV and ESR: technical aspects
Plasma viscosity
Unaffected by time-induced deterioration and can
be analysed up to 1 week post sampling
Unaffected by anaemia
Variations in red cell size and shape have no
effect
All results are universally comparable.
Calibration using fully traceable, CE marked
reagents
External Independent Quality Control is available
(Central Quality Assurance Scheme QEH.
Birmingham UK.)
Time factor: from receipt of sample, centrifugation
and testing takes 10 minutes if lab is notified in
advance
ESR
Must be analysed within 4 hours of sampling
unless EDTA sample, which has a 24 hour time
limit
Affected by anaemia
Red cell size and shape variations affect the rate
of sedimentation
Results not universally comparable due to
different anticoagulants, tubes and timing
methods.
No Independent Quality Control possible.
Time factor: from receipt of sample, setting up
and reading of result takes 65 minutes
Benson Viscometers Ltd
SAMPLE LETTER
2012
REFERENCES
1. G. D. O. Lowe. Should Plasma Viscosity Replace the ESR? : British Journal Of
Haematology, 1994; 86, 6-11.
2. Orrell R W & Johnson M H (1993). Plasma viscosity and the diagnosis of giant cell
arteritis. Br. J. Clin. Pract. 47(2):71-2
3. Gudmundsson M, E. Nordborg, B-A, Bengtsson, A, Bjelle. Plasma Viscosity in Giant
Cell Arteritis as a Predictor of Disease Activity: Annals of the Rheumatic Diseases 1993;
52: 104-109.
4. Gudmundsson M & Bjelle A (1995). Plasma viscosity in the monitoring of therapy in
rheumatoid arthritis patients. Scand. J. Rheumatol. 24(4):219-24.
5. International Committee for Standardization in Haematology (Expert panel on
Rheology). Guidelines on selection of laboratory tests for monitoring the acute phase
response: Journal of Clinical Pathology, 1988; 41: 1203-1212
6. T. Ng. Erythrocyte Sedimentation Rate, Plasma Viscosity and C-Reactive Protein in
clinical Practice: British Journal of Hospital Medicine 1997; 58: 521-523.
7. H. A. Bird, W. Esselinckx, A. S. Dixon, et al. An Evaluation of Criteria for Polymyalgia
Rheumatica: Annals of the Rheumatic Diseases 1979; 38: 434-439.
8. G. P. H. Brittain, G. G. Mcilwaine, J. A. Bell, J. M. Gibson. Plasma Viscosity or
Erythrocyte Sedimentation Rate in the Diagnosis of Giant Cell Arteritis: British Journal of
Ophthalmology 1991; 75: 656-659.
9. G. D. O. Lowe. Blood Rheology, Haemostasis and vascular disease: Haemostsis and
Thrombosis ,3rd edition (edited by A. L. Bloom, C. D. Forbes, D. P. Thomas and E. G. D.
Tuddenham); 1169-1188. Caryl Churchill Livingstone Edinburgh.
10. Paulus H E et al. (1999). Equivalence of the acute phase reactants C-reactive protein,
plasma viscosity, and Westergren erythrocyte sedimentation rate when used to calculate
American College of Rheumatology 20% improvement criteria or the disease activity Score
in patients with early rheumatoid arthritis. Western Consortium of Practicing
Rheumatologists. J.Rheumatol. 26(11):2324-31.
11. Gertz M. A. and Kyle R. A.: 1995 Hyperviscosity Syndrome. Journal of Intensive
Care Medicine 10 128-141.