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Covid-19 Plasma Viscosity Testing and Monitoring



There is a world wide demand for a test that can be used for support with the diagnostics, care and monitoring of Covid-19 patients. In the UK there is growing interest to investigate the role blood Plasma Viscosity (PV) testing has to play in relation to Covid-19. PV testing is a highly accurate indicator of many conditions including those that stimulate the immune response causing inflammation and some viral infections.



From questions being asked it appears that a rapid co-ordinated investigation in to the potential use of the Plasma Viscosity test could be easily undertaken to establish

  1. Is the PV result from Covid-19 patients abnormal?
  2. Is there a cut off value for PV to differentiate between Covid-19 patients that will recover with minimal medical intervention and those that require more aggressive intervention?
  3. The identification of recovered patients with high titre (concentration of) antibodies for donors.

These questions can be answered quickly as the PV test is well established in many NHS hospitals including some at the forefront of our fight against Covid-19 such as UCLH and St Thomas’s in London.

A person demonstrating symptoms of inflammation will have an increased plasma viscosity. The Plasma Viscosity test could be specifically used as part of local Covid-19 screening blood work and also to monitor the intensity and progress of the virus episode in a patient, especially given most hospitalised Covid-19 patients are already having daily haematology and chemistry profiles carried out.

For obvious safety reasons laboratories are applying the principles of ‘closed vial sampling’ more rigidly now and as a result, any test/sample on a Covid-19 patient that is underfilled or requires the sample top to be removed, is generally refused unless in exceptional circumstances. The PV analysis is carried out without removing the sample tube cap so is ideally suited to the current circumstances and will provide rapid and straight forward numerical results. There is one normal range for all ages and both sexes (1.5 to 1.72mPA.s) which is already well established and documented for over 50 years, meaning results interpretation is straight forward and there is no requirement to establish a normal range.

PV is an inexpensive test that is capable of a precise result with a high level of confidence within minutes of getting a blood sample to the Hospital Laboratory. All the NHS Clinical Viscometers in use are manufactured and supplied by a British company. They are already operational at this moment, programmed and linked via the NHS ‘LIMS’ (a Laboratory Information Management System Software) enabling hospitals to effectively manage samples and automatically communicate results and associated data. Therefore, obtaining results for a multi-center trial is easy.

A symptomatic or confirmed person with Covid-19 will probably have an increased plasma viscosity above the normal range. The patient’s result is likely to continue rising if their condition deteriorates until their immune response successfully has the infection under control.  Patients who have results that plateau at a relatively low level may need less intrusive therapy, while patients whose results continue to rise may require more aggressive therapy, such as oxygen support either in the form of CPAP or IPPV (ventilation). Hence early intervention could increase the likelihood of early recovery.

As one of the parameters that raises the PV result is the concentration of antibodies in a person’s plasma, it may be possible to identify recovered patients with high antibody titres by a continually raised PV after clinical recovery, thus identifying individuals suitable for plasma pheresis to provide antibody protection to other patients.

Whilst the patient is in recovery, the plasma viscosity result is likely to begin to fall, but paradoxically patients are most likely to still have a positive antigen test.  It is proposed that the start of the reduction in viscosity, when measured on consecutive days, could be used as an indicative marker for patient recovery.  Hence the patient and their relatives could be informed potentially earlier than at present that their recovery has begun, thus reducing anxiety for clinicians and families. If a daily PV monitoring routine is started as early as practical, a record of the Covid-19’s progress will be available to aid clinicians in determining the most appropriate treatment and with data analysis and experience will be able to forecast and prepare for a worsening condition if the data shows a patient in a deteriorating situation.

Furthermore, when a person first develops the symptoms or is suspected of having Covid-19 there may potentially be a larger increase in viscosity in some patients than in others.  If the percentage increase is above a particular value this could also be a potential indicative early marker that these patients may subsequently need further oxygen support either in the form of CPAP or IPPV (ventilation).  Hence early intervention could increase the likelihood of early recovery.

Moving forward, there is going to be a lot of research, statistical analysis and “lessons learnt” from this pandemic. The PV test will play a significant part in that, as both an individual test, and as part of a routine blood work up panel. To facilitate this, there now needs to be as many PV tests performed as possible to provide large volumes of meaningful data which can be evaluated and statistically analysed to assist with Covid-19 but also with any future pandemics. Many laboratories have a much-reduced workload volume now and have also altered their working practices. This is an opportune time to utilise that capacity and the existing equipment to support the UK being the leader in finding the answers to Covid-19

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