Plasma is a yellow coloured liquid that is the liquid part of blood and it contains antibodies involved in regulating immune responses. Convalescent plasma therapy is an experimental medical procedure, where critical Covid-19 patients are treated using plasma collected from those who have recovered from the viral infection. The treatment was also used for MERS and Ebola.
According to an article in the journal Nature, Michael Joyner, an anesthesiologist at Mayo Clinic in Rochester, Minnesota, said researchers have struggled to nail down its effectiveness in the middle of the pandemic. First, it is challenging to study this as antibody concentration varies in different people.
A study funded by the US government was conducted by Mayo Clinic in which 35,322 patients who received plasma transfusions. It was an open-label observational study, in which the participant and researchers know what treatment is being administered. The three-month open-label study found overall mortality lower for patients who received plasma.
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But the fact that this study was conducted with no control group or placebo group was a huge limitation as it could have helped determine the efficacy of plasma therapy. Since convalescent plasma has been tested only in small trials it does not have the statistical power to provide firm conclusions.
In India, convalescent plasma therapy has shown encouraging results. In an IANS report, Rahul Bhargava, Director, and Head, Haematology at Fortis Memorial Research Institute in Gurugram stated that the data has been equivocal with many confounding factors.
“Only a properly well-randomized controlled trial will help to know which patient at what time/duration of disease and the extent of disease will get benefitted. In the past also, for various diseases, plasma therapy has been utilised with great success and failure,” said Bhargava.
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Indian Council of Medical Research (ICMR) is conducting a trial called PLACID to test the effectiveness of plasma therapy. It is a Phase II, open-label, randomised controlled test with a sample size of 452.
In an article by Indian Express that a total of 52 institutions are involved in the trials. The daily spoke to 36 institutions out of which 24 said plasma therapy was effective. The ICMR is yet to publish the results. But the interim analysis by AIIMS has found no effect on mortality rates.
Dr. Satya Prakash Yadav, Head of Pediatric Hematology, Medanta Hospital in Gurugram said in an IANS report, “The use of convalescent plasma collected from previously infected individuals to passively-transfer antibodies in order to protect or treat humans dates back almost 100 years.” He added “Many patients improved clinically and cleared the virus.
However, the role of the convalescent plasma treatment in these patients is unclear because all patients received at least one additional therapy, including antivirals, antibiotics or antifungals, and corticosteroids.” Dr. Yadav stressed on the importance of more randomised controlled trials to confirm the benefit of plasma therapy for severe Covid-19 patients.