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Convalescent Plasma Therapy & COVID-19 - All you need to know about it

The convalescent plasma therapy has been used to treat people with severe COVID-19 caused by the novel corona virus or SARS-Cov-2 virus. With no vaccine or specific treatment for the dreaded virus, researchers are exploring various approaches – such as convalescent plasma therapy – to fight the respiratory illness. The experimental therapy has shown to be beneficial in some COVID-19 patients, including in India.

But, what is plasma therapy and how it can be useful is a common question lingering in most people’s mind. Here is all you need to know about it.

What is plasma and what is its function

Plasma is the pale yellowish liquid part of the blood that holds the blood cells in whole blood in suspension. It carries protein, minerals, nutrients and hormones to the different parts of the body. It makes up about 55 per cent of the body’s total blood volume. Plasma itself is made up of 90% water, the remaining portion is composed of proteins such as albumin, gamma globulin, anti-haemophilic factor, and mineral, salts, sugars, fats, hormones and vitamins. The major function of plasma is to maintain normal blood pressure, supply proteins to different parts of the body for blood clotting and immunity, carry electrolytes such as sodium and potassium to our muscles and to maintain a proper pH balance in the body.

How plasma therapy helps COVID-19 patients?

This therapy’s concept is simple and is based on the premise that the blood of a patient who has recovered from COVID-19 contains antibodies with the specific ability of fighting novel coronavirus. The theory is that the recovered patient’s antibodies, once ingested into somebody under treatment, will begin targeting and fighting the novel coronavirus in the second patient.

The convalescent plasma therapy is akin to passive immunisation as, according to researchers, it is a preventive measure and not a treatment for the COVID-19 disease.

Not the First time

This is not the first time convalescent plasma therapy is being considered as a treatment for viral infections.

1. In 2014, the World Health Organisation (WHO) had recommended the use of convalescent plasma therapy to treat patients with the antibody-rich plasma of those who had recovered from the Ebola virus disease.

2. For the treatment of people infected with Middle East respiratory syndrome (MERS), which is also caused by a coronavirus, a protocol for use of convalescent plasma was established in 2015.

3. During the 1918 H1N1 influenza virus (Spanish flu) pandemic, the therapy was used experimentally.

4. The plasma therapy was used as a treatment during the H1N1 infection of 2009.
Others serious outbreaks that have seen the use of this therapy are the SARS outbreak, Measles, HIV, polio and mumps.

The technique of plasma donation

Donating plasma is not the same as donating blood. The two are different and require different techniques.

The blood donation process is simpler as compared to plasma donation. During blood donation, the whole blood is collected in a bag and its components are later separated in the laboratory. However, in plasma donation, blood that is drawn from the arm has to go through a special machine where plasma is separated from the rest of the part of the blood. Only the plasma is stored and the rest of the components including donor’s red blood cells and platelets are then returned to the body along with some saline. Due to its complexity, plasma donation takes more time than blood donation. While it takes only 30 minutes to donate whole blood, plasma donation is an hour and a half long procedure.

The collected plasma should be transfused in the patient’s body within 8 hours or it should be immediately frozen.

Fresh frozen plasma (FFP) can be stored for close to a year at -18 degree Celsius. Although plasma can be stored, but the doctors do not recommend it, as storing plasma makes the antibodies present in it less effective.

Who can donate plasma?

Those who had the disease, but have recovered at least 14 days before the donation can be considered — although doctors prefer a time of three weeks between recovery and donation. Individuals must have had a prior diagnosis of COVID-19 documented by a laboratory test while also meeting other donor criteria.

People between the ages of 18 and 60, and weighing not less than 50 kg are eligible. Women who have given birth are not eligible, as the antibodies they produce during pregnancy (after being exposed to the blood of the foetus) can interfere with lung function.

People with comorbidities such as diabetes, hypertension, and cancer are also excluded. A detailed medical history will be taken along with physical examination (height, weight, blood pressure, temperature, adequate veins for phlebotomy).

What tests are carried out before donating plasma?

Laboratory tests are carried out to assess various conditions — serum protein and CBC, TTI testing for hepatitis B virus, hepatitis C virus, HIV, malaria, and syphilis — and for blood grouping and antibody screening. Serum COVID-19 specific IgG antibody concentration higher than 80 is preferred.

How many people would be benefitted by one person’s donation?

Each plasma donation would be used to treat 2 patients. The bank collects 500 ml of plasma, depending on weight.

How often can a recovered patient donate plasma?

500 ml of plasma can be donated every two weeks, while blood can be donated once in three months. Plasma can be stored for a year, as frozen plasma will still have antibodies. The antibody level doesn’t decrease in a person’s body.

What to do before donating plasma

Here are a few things one must do before donating plasma:

  • Drink plenty of water
  • Inform if you recently had a surgery
  • Inform if you are taking any specific drugs