that serum viscosity measurement was essential for rational clinical management.7 Waldenstrom’s macroglobulinaemia is a condition that causes an increase in IgM immunoglobulin. This protein is a large, asymmetrical molecule that causes blood viscosity to rise rapidly to levels causing major organ damage. Monitoring the patient by PV analysis can lead to earlier treatment, thus reducing the risk of hyperviscosity syndrome. For those patients who do develop hyperviscosity syndrome, the treatment is frequently a plasma exchange, and, using PV to monitor the treatment, clinicians can rapidly determine if sufficient rounds of treatment have been undertaken.

Benefits realised from plasma viscosity analysis As demonstrated above, there is much in the literature to demonstrate that PV is a clinical test that can help in the diagnosis and treatment of several conditions. The test has been available for over 70 years and yet it is still not fully understood. Why?

The main reason appears to be a misconception that performing a PV test is difficult. This probably was the case until the 1980s. In the UK, Coulter Electronics developed a semi-automated plasma viscometer (Visco II) that

permitted batch analysis. Plasma was put in cups on a carousel which the machine then automatically sampled and analysed. However, the parent company did not market the device in the USA, and in the 1990s Coulter UK withdrew the product. Most of the world was therefore left to use adapted (or not) industrial viscometers to analyse clinical samples. These devices were time-consuming to use and had little or no clinical calibration. This led to a significant number of published papers reporting results as relative viscosity to that of water. Another issue has been using the

wrong type of viscometer. The Coulter Visco II was designed as a clinical instrument, calibrated within the range of plasma viscosities, and most importantly was a capillary viscometer. It also reported in SI units, meaning that all machines gave the same results for the same sample (within manufacturing tolerance). Capillary viscometers are suitable for use on Newtonian fluids like blood plasma and serum; they also have the advantage that a calibrant can be analysed with each batch or number of tests, and they can be easily cleaned automatically by sampling and processing a cleaning reagent. Historically, the USA continued to use mainly industrial cone and plate technology, which lacks the benefits

of capillary analysers. The cumbersome cleaning requirements, lack of standardisation and SI reporting units made clinicians sceptical of the results and hence the test. In recent years there has also been a drive to reduce costs within the NHS across the UK. Pathology tests were highlighted as an area associated with substantial spending. General practitioners were directed to be more selective in their requests for a diagnostic test and to reduce the number of tests they requested, as it was identified that often they would request multiple tests which, in some cases, were seen to overlap or duplicate.8 However, this activity has led to several outcomes. The ability readily to request certain tests has been made more difficult, which in turn has led to a decline in some tests being requested. This ultimately has led to inefficiencies in delivering the ability to conduct the test and a perception that these tests are expensive as there are no longer economies of scale. There has been an increased acceptance of less-appropriate tests as meeting the clinical need and a mindset of ‘it will do’. The strive for clinical excellence has been overtaken by thoughts of cost and the strategic activities to save it. While value for money

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1 0. 1 5. 2.0 2.5

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100 120 0RU/ml



Extin ionct

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