HAEMATOLOGY
Plasma viscosity: a vital monitoring role
Establishing the diagnostic and prognostic value of measuring plasma viscosity in patients suspected or confirmed as having COVID-19 is currently underway in several UK hospitals. The following article provides an overview of progress in research and practice.
The COVID-19 disease presents a rapid learning challenge for everyone involved in battling with the condition. While widely regarded as primarily a respiratory disease, it is increasingly being recognised by doctors and scientists as a systemic infection, which affects not only the respiratory tract, but also the central nervous system, musculoskeletal, renal, haematological and hepatic systems. The haematological clinical
manifestations of COVID-19 are receiving increasing attention, as the scientific and medical community work hard at trying to solve some of the many questions posed. For example, why is it that some patients have severe symptoms while others have relatively mild symptoms? What is the pathology of the emerging phenomenon of the Kawasaki- like illness linked to COVID-19, which has coronary artery aneurysms as its main complication?1
Why do a substantial
proportion of severe COVID-19 patients develop venous and arterial thromboembolic conditions, and what can we do to improve early recognition of these?2
Haematological
investigations are going to be critical to solving these and other emerging questions. Many of the supporting answers could lie in plasma viscosity.
Plasma viscosity testing
Plasma viscosity testing is a sensitive index of plasma protein changes that result from inflammation or tissue damage. The plasma viscosity (PV) test is well-established in many NHS hospitals, including some at the forefront of the fight against COVID-19, such as University College Hospital and St Thomas’ Hospital in London, and Addenbrooke’s Hospital in Cambridge. It is a highly accurate indicator of many conditions including any inflammatory disorder (eg infection, rheumatoid arthritis), tuberculosis and polymyalgia rheumatica/ temporal arteritis. It is also used as a
OCTOBER 2020 Plasma viscosity at University College Hospital in London using BV1 and BV200.
marker for subsequent adverse events in angina, stroke and peripheral occlusive vascular disease. Plasma viscosity is used
The plasma viscosity test is well-established in many NHS hospitals, including some at the forefront of the fight against COVID-19
as a screening test but, unlike some other indicators and inflammatory markers, it is not affected by haematocrit variations (eg anaemia or polycythaemia) or gender, patient age, exercise, pregnancy and age of sample. Many clinicians recommend the PV test for its sensitivity. Other benefits of the test are that PV becomes abnormal early in the disease, has a low incidence of false-normal values, can be performed on a sample up to seven days old, is stable, technically reproducible and standardised, and that relatively small changes are significant for any individual.
As with any infection, SARS-CoV-2 will cause an increase in the release of acute- phase proteins into the circulation. Plasma
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