BLOOD SCIENCES


in multiple myeloma (can result in) dramatic relief in symptoms from the lowering of viscosity by plasmapheresis’. In this paper the authors discuss both PV and SV testing, to which both are found to have clinical significance when screening for MM (Wright and Jenkins, 1970).17


Changes in plasma viscosity and other blood test parameters can be detected up to three years prior to myeloma diagnosis. Koshiaris et al. (2018) conducted a five-year prospective study of 2,703 patients with myeloma and 12,157 in a healthy control group.18 The study showed that the Hb began to fall up to three years before diagnosis, the MCV began to increase up to one and a half years before and the PV began to show an increase up to two years prior to diagnosis. The authors looked at individual parameters and combinations to obtain ‘likelihood ratios’ to rule in or rule out myeloma. It was found that PV had higher rule-in and rule-out sensitivities than ESR. However, they found that the rule out likelihood ratio using a combination of Hb and PV was the best, with 95% sensitivity. This rose to 97% when creatinine was also added. The authors concluded that: “ESR and PV have better diagnostic performance for myeloma both as rule-in and rule-out tests when normal in contrast to CRP which has very little value in myeloma diagnosis.” Given the variables associated with ESR and the relative stabilities of the PV there is evidence that a screening programme using Hb, PV +/- creatinine may be beneficial.


n Waldenstrőm’s macroglobulinaemia Waldenström macroglobulinaemia is an indolent lymphoma (ie one that tends to grow and spread slowly) and a type of lymphoproliferative disorder which shares some clinical characteristics with the indolent non-Hodgkin lymphoma.19


It is


commonly classified as a form of plasma cell dyscrasia, similar to other disorders in this group, such as those that lead to multiple myeloma.


It was first described by Jan Waldenström in 1944 in two patients Factors Normal range is consistent across different ages and genders


Unaffected by physiological stimuli: lifestyle, smoking, weight, blood pressure Anaemia and polycythaemia do not interfere with the result Testing can be performed on a sample up to seven days old Aspirin and steroids have no effect on the result


Can be a diagnostic test for: Multiple myeloma, hyperviscosity,


temporal arteritis and Waldenström’s macroglobulinaemia Reliable, repeatable and reproducible test results


Table 2. ESR, CRP, PV and SV comparison table.


who presented with bleeding from the nose and mouth, anaemia, hypofibrinogenaemia, lymphadenopathy, neoplastic plasma cells in the bone marrow, and increased blood viscosity due to increased levels of macroglobulin.20


Until the late 1990s, WM was


considered to be related to multiple myeloma due to the presence of a monoclonal gammopathy and infiltration of the bone marrow and other organs by plasmacytoid lymphocytes. However, the World Health Organization (WHO) now classifies WM as a lymphoplasmacytic lymphoma, which is itself related to non- Hodgkin lymphomas.21 Presenting symptoms of WM


are heterogenous but often include weakness, fatigue, weight loss, blurring or loss of vision, nystagmus, chronic oozing of blood from mucous membranes of the nose and gums, peripheral neuropathy, hepatosplenomegaly, headache, and rarely stroke or coma.22


It is characterised by an uncontrolled


clonal proliferation of B lymphocytes with >10% lymphoplasmacytoid cells in the bone marrow. Genetic mutations have been discovered, the most common being MYD88 and CXCR45. CXCR4 mutations are known to cause symptomatic hyperviscosity syndrome.23 There is also thought to be a two-to-


threefold increased risk of Waldenström macroglobulinaemia in people with a history of autoimmune diseases with autoantibodies, and a particularly elevated risk associated with hepatitis, HIV and ricketts.24


Hence there is a case for including


regular plasma viscosity screening in this patient group.


n Hyperviscosity due to cellular components


The cellular components of blood can also contribute significantly to HVS; an increase in haematocrit (polycythaemia) being the most common. Polycythaemia can be broadly classified into two types: primary polycythaemia (polycythaemia rubra vera [PRV]) and secondary polycythaemia. Alternatively, the ‘absolute polycythaemias’ refer to an increase in haematocrit and/or haemoglobin whilst the ‘relative polycythaemias’ refer to a decrease in plasma volume caused by other reasons such as dehydration, cardiorespiratory or renal problems. PRV is a myeloproliferative disorder typically with a haematocrit above 0.55,25 leading to an increase in whole blood viscosity (WBV) and is most commonly found in the over 60 age group26


with


males more commonly affected than females.27


Secondary polycythaemia can be caused by tissue hypoxia induced by cardiorespiratory problems, long- term smoking and over secretion of erythropoietin due to renal or drug related causes. Other cellular influences on blood viscosity are red cell deformability and aggregation, which is enhanced where vascular bifurcations are found, or in the presence of vascular plaques.


Red cell rigidity (the inverse of deformability) can be calculated from whole blood viscosity, plasma viscosity and haematocrit using an equation by Dintenfass


34


Red cells are a biconcave disc shape and have a resting diameter of approximately 7.5µm whereas nutritive capillaries have a diameter as low as 3µm. Therefore, the ability of red cells to be flexible is of crucial importance to maintaining fluidity of blood and therefore perfusion of the capillaries in all organs and tissues. Furthermore, normal red cells can immediately regain their resting shape, diameter and functionality, repeating the process many times for the duration


DECEMBER 2025 WWW.PATHOLOGYINPRACTICE.COM ESR CRP PV SV


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