A well-known head and neck surgeon explains why doctors are using
The convalescent plasma is getting a lot of media coverage because it is being used to treat politicians and actors testing positive for COVID-19. Many even confuse it as a cure to the
What is plasma
A straw coloured fluid blood component, the plasma transports antibodies, nutrients and hormones to parts of the body that need it.
What is convalescent plasma?
Convalescent plasma, also known as passive or ‘borrowed’
IgM abtibodies are formed by
Antibodies transferred through transfusion of convalescent plasma provide immediate immunity to those:
(a) In imminent danger of COVID-19 infection.
(b) Those who are already affected by COVID-19 infection.
In the past, convalescent plasma has been used in two other occasions. First, the coronavirus epidemics of SARS1 in 2003 and second, MERS in 2012. Experience with convalescent plasma in those epidemics demonstrated that it contains neutralising anti-bodies and the results were encouraging. These patients were able to get off the ventilator, demonstrated impressive reduction in viral loads, their oxygen levels improved and the patients stabilised clinically.
It is important to know that the efficacy of convalescent plasma is unproven for COVID-19 and is only at an experimental stage.
How does one avail convalescent plasma?
Currently it is available under three categories (a) Given on compassionate grounds, (b) Used as part of a trial (c) Is administered through an institution like a university/government run hospital.
How is it collected?
Plasma can be collected from the donors using either of these methods.
1 Apheresis — a process where the whole blood is continuously centrifuged into its components (ie red blood cells, plasma, platelets). This permits selective collection of the plasma, allowing the other components to be returned to the donor. It requires special equipment to do so, which may not be easily available.
2 It is extracted from whole blood.
How to be a convalescent plasma donor?
1 The donor should have completely recovered.
2 IgG antibodies should be elevated. The concentration of antibodies should be above 1:80 and rising. (1:160 is considered acceptable for a donor.)
3 SARS-CoV-2 infection should be confirmed by a valid and official diagnostic test at the time of illness.
4 A donor needs to wait for 14 to 28 days to recover fully before being allowed to donate.
5 Standard selection criteria is required to rule out HIV, Hepatitis B, HCV, syphilis etc.
6 To avoid the risk of Transfusion Related Acute Lung Injury (TRALI) preference should be given to use plasma from male donors. Female donors who have never been pregnant may be considered. This is because pregnancy can cause antibodies to HLA or granulocyte antigens that cause TRALI (transfusionrelated acute lung injury), which can be disastrous.
Criteria to be a donor
1 The donor should not have fever.
2 No respiratory problems.
3 Normal oxygen levels.
4 Good health with no other problems.
5Two non-reactive (negative) Nucleic Acid Tests (NAT) for SARS-CoV-2 performed at an interval of at least 24 hours on nasopharyngeal swabs.
6 Antibodies should be present.
The total and neutralising titers of anti-SARS-CoV-2 antibodies should be determined. The volume of plasma collected should be between 200 ml to 600 ml. Should the donor wish to donate plasma again through the apharesis method it should be done after seven days. If the donor has donated whole blood then he/she has to wait for at least eight weeks before the next plasna donation.
Once extracted the convalescent plasma should be frozen as soon as possible at -20°C or preferably colder and stored until administration.
It is crucial to ensure ABO and Rh compatibility between the donor and the recipient.
Recipient patients should receive an initial dose of 200 ml, followed by one or two additional doses of 200 ml according to the severeity of the disease and tolerance of the infusions.
How does convalescent plasma act?
1 The antibodies bind to the virus, thus, neutralising it.
2 The antibodies then act on the mediated pathways such as complement activation, antibodydependent cellular cytotoxicity and help prevent / lessen damage to cells.
3 Phagocytosis of (where the white blood cells attack and engulf) the virus.
4 Transfusion of plasma from at least two donors provides diverse antibodies offering greater immune protection.
5 Viral load is reduced.
The risks to transfusion recipients are not significantly different from those receiving standard plasma. Transfusion associated circulatory overload (TACO) occurs when too many fluids are infused. This can occur if the patient has pre-existing heart disease. That’s why convalescent plasma is preferred over whole blood transfusions.
How long can it be stored?
Plasma frozen at -18°C or colder within 24 hours after blood collection can be stored for up to 12 months.
Convalescent plasma is an experimental therapeutic agent in the treatment of COVID-19. It should be available with other current therapies.
The author is an assistant professor in ENT surgery, University of New York and Louisiana State University Medical Centre, USA