BLOOD SCIENCES
individuals aged three years and above is considered to be, a result within 1.50 - 1.72 mPa.s reported at 25°C (room temperature) and 1.12 - 1.27 mPa.s reported at 37°C. Importantly a minor variation in a patients PV of 0.05 mPa.s is deemed to have clinical significance.30 Plasma viscosity is widely used by scientists and clinicians in diagnosing and monitoring a host of complex clinical conditions. Most commonly:29 n Polymyalgia rheumatica n Rheumatoid arthritis n Temporal arteritis n Hyperviscosity syndrome n COVID-19 n Multiple myeloma n Waldenström’s macroglobulinemia n Cardiovascular disease n Diabetes n Vascular dementia n Alzheimer’s disease n Sepsis.
The PV results are able to provide an earlier indication of the requirement for specialist care for COVID-19 patients, with a probable need for intensive care (ICU) and a subsequent chance of increased survival.
from the normal. The plasma viscosity test is extremely sensitive in distinguishing between inpatients exhibiting symptoms of COVID-19 and those who do not. The PV results provide an earlier indication of the requirement for specialist care, with a probable need for intensive care (ICU) and a subsequent chance of increased survival. Consequently, it enables the allocation of additional resources to be focused on patients who genuinely require them, rather than those patients testing positive but with a lower risk.
This effective and simple test will
provide essential information in risk- stratifying patients who present with symptoms of COVID-19. There have been no other reported laboratory tests, which have been able to quantify the degree of disease burden to this level of accuracy. According to the Gleghorn et al., (2021) the Addenbrooke’s COVID-19 study, it is evident that PV is an extremely sensitive and dependable test. This test has the potential to serve as a clear biomarker for monitoring patients with
long COVID symptoms. Using the data from the study, it
introduces the possibility that patients who presented with a PV of 1.83 mPa.s or more, reported at 25°C – and therefore at high risk of hospitalisation – could be monitored by PV measurement regularly up to one year after the initial infection to assess the possibility of long COVID.
Measurement of plasma viscosity Since the introduction of efficient measurement of plasma viscosity (PV) as detailed by Harkness in 1971; PV testing has been available in many haematology laboratories.28
Plasma viscosity is
renowned as a quick, inexpensive, non- specific test, but also capable of being a more accurate and useful screening test. The viscosity of plasma is determined by the concentration and size of proteins in the blood which increases as part of the body’s normal response to infection, inflammation, and due to the effects of traumatic injury.29 The PV normal reference range for
Based on scientific studies, the plasma viscosity test is a robust and reliable tool that provides valuable insight into a patient’s health, particularly in relation to inflammatory and haematological conditions.31
The PV test has advantages in terms of
stability, direct measurement, and minimal external factor interference. This makes it a superior choice in detection of elevated proteins and also abnormal paraproteins in many clinical scenarios. Therefore, the PV test is far more valid, accurate and sensitive than the C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) tests.
Conclusions Plasma viscosity test results are reliable, repeatable, and reproducible. The benefits and rewards of PV testing are substantial, for clinical services and for the patient’s clinical outcome. Plasma viscosity measurement can add useful information in the diagnosis and treatment of various disorders. Most notably in the diagnosis and treatment of long COVID, when used to detect the continuing and active pattern of inflammatory proteins in the blood. Therefore, it is recommended that the plasma viscosity test should be exploited and utilised more frequently in clinical practice.
Plasma viscosity will aid in risk-stratifying patients who present with symptoms of COVID-19. There have been no other reported laboratory tests which have been able to quantify the degree of disease burden
WWW.PATHOLOGYINPRACTICE.COM SEPTEMBER 2025
References 1 Mayo Clinic. Coronavirus disease 2019
(Covid-19). (Mayo Clinic, 2024).
www.mayoclinic.org/diseases-conditions/ coronavirus/symptoms-causes/syc- 20479963
2 Johnson TJ, Nishida RT, Sonpar AP, et al. Viral load of SARS-CoV-2 in droplets
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