Why testing blood thickness could be an important step in Covid-19 treatment

A unique type of blood testing equipment manufactured by a small company in West Wales is emerging as an important tool for understanding how Covid-19 affects the body and for choosing the best treatments for patients.

Benson Viscometers designs and manufactures blood viscometers which, put simply, measure the thickness of blood. In June, doctors at Emory University in the USA, hit on the idea that blood thickness (or viscosity) might be an important pointer for deciding how to treat Covid-19 patients. They had noticed that many Covid-19 patients had unusual blood clotting that did not respond to the usual anti-clotting medication.

“We were unsettled by the fact that some patients with severe Covid-19 had atypical blood clots, even when therapeutically anticoagulated,” says Cheryl Maier, Assistant Professor of Coagulation and Transfusion Medicine, Department of Pathology and Laboratory Medicine, Emory University School of Medicine and medical director of Emory’s Special Coagulation Laboratory. 

“This prompted us to consider other causes of clot formation, like hyperviscosity, which can be detected by plasma viscosity testing. We found that the sickest patients with Covid-19 had the highest plasma viscosity levels, more than twice normal levels. We also found that patients with the highest viscosity levels were more likely to have a blood clot. We think that the inflammation caused by SARS-CoV-2 infection causes the hyperviscosity, which may contribute to blood clots in some patients.”

She adds that the viscosity levels in the sickest Covid-19 patients were similar to those seen in a type of blood disorder called hyperviscosity syndrome, where the high viscosity leads to dangerous sludging of the blood in the brain and other organs.

“We need larger studies to understand whether hyperviscosity is simply a marker of severe Covid-19 or actually contributing to blood clots in these patients,” she says. “Nevertheless, we’re trying to determine any beneficial role of lowering the viscosity in these patients through a treatment called plasma exchange.”

In the UK, Addenbrookes Hospital is using Benson Viscometers’ equipment to explore how best to understand and treat Covid-19. They have been carrying out the test on all suspected Covid-19 patients to establish a link between PV (plasma viscosity) and Covid-19 and to explore how plasma viscosity relates to the severity of and/or recovery from the disease.

“The tentative results so far, prior to sufficient statistical analysis, clearly show that there is an increase in the PV level associated with a positive Covid result. This is in line with what we would expect,” says Daniel Gleghorn, Senior Biomedical Scientist – Automation Lead, Clinical Haematology, Cambridge University Hospitals NHS Foundation Trust.

“I believe the PV test has potential as a useful marker in the diagnostic assessment of patients with suspected Covid-19 and for monitoring disease progression.”

He adds that the PV test has some important advantages over other tests that are used to detect inflammation, including cost and availability.

“From a laboratory management perspective, it is well documented that the PV test provides a more useful indicator of infection, inflammation and malignancy than the traditional ESR,” he says. “It is also a cost-effective test compared with other expensive biochemical methods, can be performed on the same EDTA tube used for a full blood count and is quick and easy to perform.

“There is also the benefit of a less complicated and reliant supply chain for consumables and reagents. This has been significantly affected for other tests (CRP, procalcitonin and Interleukin-6) where this is not the case due to a worldwide increase in demand and the effects of lockdowns on distribution networks.”

Meanwhile, Health Services Laboratories in London is also on the case. HSL is a partnership between the Australian company TDL (The Doctors Laboratory), UCLH (University College London Hospitals NHS Foundation Trust), The Royal Free London NHS Foundation Trust and North Middlesex University Hospital.

HSL’s flagship laboratory, ‘The Halo’ in London (one of the largest pathology laboratories in Europe) is using the plasma viscosity test to monitor inflammatory status in certain groups of Covid-19 patients, and is exploring the possibility that high inflammatory markers might indicate the need for alternative strategies for stroke prevention in these patients.

“The aim is to get an overall insight on the reoccurrence of strokes despite patients being on antiplatelet medication and to identify the battery of tests available that can help in these cases,” says Deepak Singh, Head of Department, Haematosis, at Health Service Laboratories.

For Benson Viscometers, these developments have led to heightened interest in the clinical analysers the company has been making for over 20 years. Demand for viscosity testing has now risen so much in the light of Covid-19 that the company is about to take on an additional development premises in Haverfordwest.

Bernie Benson, who created Benson Viscometers, is pleased to see his equipment helping to shape the understanding of Covid-19 and the development of effective treatments.

“It is encouraging to see the growing intensity and vigour of interest in blood and blood plasma viscosity which has been generated by the demand for answers on how to combat the coronavirus,” he says. ” We are able to apply our ingenuity and ability to adapt and respond to the rapidly changing demands and needs generated as a result of this global pandemic.

“The plasma and serum viscosity test is highly valued and routinely used by many eminent UK hospitals for a range of conditions, and it is exciting to see how blood viscosity tests are now being utilised in the USA.”

Looking to the future, there is clear potential that the wider use of these blood tests will lead to a significant improvement in the outcome for critically ill patients and that the high value of this approach will be recognised.

“Covid-19 is not going away, well at least not for the next few years,” says Daniel. “There is however, a need for a diagnostic and prognostic testing strategy not just for the short term, but for many years ahead. If it can be proven that a PV test can be used as part of a diagnostic algorithm, possibly as a positive predictive indicator for Covid-19 it may then form part of a recognised battery of tests for this purpose.

“In addition, determining the prognostic value of PV will hopefully provide an aid to clinicians showing a potential improvement or deterioration in the patient’s condition. The clinicians can then act appropriately in a timely manner. Plasma viscosity at point of care for these patients may also be a possibility.”