With the country battling a pandemic and researchers and doctors still trying to find a cure, there are a lot of questions regarding the best treatment for Coronavirus. One among them is plasma therapy for patient recovery. While a section denies its efficacy, social media platforms are full of messages seeking information on suitable plasma donors.
“One needs to understand that this infection is entirely new for us and countless researches are taking place across the globe. Hence developing a basic understanding is the key instead of getting influenced by any misconception,” said Dr Gitali Bhagawati, consultant and head, Department of Microbiology and Infection Control, Dharamshila Narayana Superspeciality Hospital.
What is Convalescent plasma therapy in SARS CoV-2?
In SARS-CoV-2 infected individuals, 90-99 per cent of individuals develop detectable neutralising antibodies within four weeks following infection. Convalescent plasma therapy (CPT) uses blood from people who’ve recovered from a Covid-19 infection. Basically, it is a method of passive immunity where there is a transfer of antibodies from an individual who has recovered from the disease to a person who has not developed their own antibody response yet.
“In the early part of Covid-19 infection, there was great enthusiasm for donating plasma by voluntary donors after recovery from Covid-19 infection. This was because of its great benefit during 1918’s influenza pandemic. Some people develop more neutralising antibodies after Covid-19 infection. Plasma derived from such individuals is called High titre convalescent plasma or HTCP. Similarly, less antibody carrying plasma after the disease is called Low titre convalescent plasma (LTCP),” Dr Bhagawati told indianexpress.com
In Covid-19 infection, some randomised controlled trials done amongst moderate to severely ill patients, no clinical efficacy was found with convalescent plasma. ICMR conducted a multicentre randomised controlled trial across 39 public and private hospitals on CPT amongst 464 moderately ill laboratory-confirmed COVID-19 affected individuals. No benefit of CPT could be established.
“Some observational studies, however, showed some modest clinical effects were observed. That is why, Food and Drug Administration (FDA) approved convalescent plasma for hospitalised Covid-19 patients with signs of progressive infection,” said Dr Bhagawati.
Some found that early administration of high-titer convalescent plasma against SARS-CoV-2 to mildly ill infected older adults reduced the progression of Covid-19.
Observational data suggest a benefit of COVID-19 convalescent plasma in patients with various immune-deficiency diseases, like primary and secondary humoral immunodeficiencies (eg, IgA deficiency, multiple myeloma etc.)
Selection of donors
Donor must be previously infected with SARS CoV-2; minimum after two weeks of infection. Whenever convalescent plasma therapy is recommended, antibody level against Covid-19 has to be checked. IgG antibody persists for a long period as compared to IgM. Therefore, level of IgG has to be checked.
IgG antibody varies in different individuals after Covid-19 infection. It is found in various studies that HTCP is found to be more effective than that of LTCP.
Level of IgG antibodies may vary in different platforms of testing methods also (eg, ELISA, CLIA etc)
Plasma should be screened for other viral markers like Hepatitis B and C virus and HIV.
Take home message
Although CPT is in use in Covid-19 infection, in large randomised controlled studies, no such role has been documented for patients with moderate to severe infections. “Therefore, we should not panic if somebody on mechanical ventilator is not getting convalescent plasma,” she said.
Vaccination and other Covid appropriate behavior are key to preventing the disease. Awareness regarding these is adequate amongst all but we need to implement it in our attitude.