The FDA recently issued an emergency authorization used for doctors to treat COVID-19 using convalescent plasma from patients who’ve recovered from the disease. But researchers and doctors are concerned that this push to distribute convalescent plasma could undermine the clinical trials needed to determine whether it actually works against this coronavirus.

Link for absolute and relative risk reduction:
https://bestpractice.bmj.com/info/toolkit/learn-ebm/how-to-calculate-risk/

Link to the main study in the video:
https://www.medrxiv.org/content/10.1101/2020.08.12.20169359v1

In order to understand the science behind what is going on with convalescent plasma, we first have to understand what is convalescent plasma, and how plasma for COVID 19 working. Then I’m going to talk about my experience giving it to coronavirus patients, and what the studies are actually showing.
When someone is infected with COVID-19, and they recover, they then develop antibodies, typically within a few weeks. How long these COVID-19 antibodies last, and how effective they are against the virus, is a whole nother conversation.

But these IgM and IgG antibodies are in the bloodstream, and when we draw blood from a patient who has recovered from COVID, that blood then gets spun in a centrifuge and collected. A certain portion of that blood is called plasma. And in that plasma are the immunoglobulins, including IgG and IgM antibodies. The rest of the blood, mainly red blood cells and platelets, is used for…blood transfusions. So with the plasma that we collect, that’s what contains the COVID-19 antibodies to the virus, and then we give that to hospitalized COVID patients. They did this for some patients with SARS and MERS and had good results. Then, in 2009, an observational study of over 90 critically ill patients with H1N1 influenza A, 20 of those patients received convalescent plasma. The ones who received the plasma had better survival rates.

In theory, the COVID-19 patients who would most likely benefit from this would be the ones who get the plasma as soon as they are diagnosed with COVID in the hospital setting. The sooner they get it, the higher the likelihood of it being effective. At least in theory. Also, the higher the number of antibodies in the plasma, the more likely it is to be effective. At least in theory.

Although some US hospitals have already been giving plasma for COVID-19 in special cases, an emergency-use authorization from the FDA would make it easier to give it to more and more patients. My hospital is part of a clinical trial for CPT, and we’ve been giving it to COVID patients. Based on my experience, its hard to know if it makes any difference at all. I can tell you, that there has not been one patient who I’ve given it to, and all of a sudden, within a day or two, they are much improved.
I’ve given it to many patients, and there have been good outcomes and bad outcomes, and everything in between. For the patients who did improve, was this because of the CPT? Was it because of the dexamethasone they received? Or Remdesivir they received? Or tocilizumab? Or was it just a coincidence and they were going to get better regardless? Or is it some sort of combination of these? Impossible to know.

The only real way to know if any of these treatments make any kind of difference is to have randomized control trials that involve lots of patients. So far, there are no RCT for CPT. Based on the published observational studies we have so far, there’s little evidence to suggest that CPT actually helps patients.

Convalescent plasma has been tested only in small trials without the statistical power to provide firm conclusions. Another consideration is that convalescent plasma from different people varies widely in antibody concentration, meaning different amounts of antibodies. So on a person might receive fewer antibodies than someone else. And on top of that, we don’t even know how effective these antibodies are, meaning, are these antibodies ‘neutralizing antibodies.’ The Biomedical Advanced Research and Development Authority (BARDA) in the US has provided convalescent plasma on this basis to more than 70,000 people, but this was done without having any control groups, meaning these were not RCT. But this statement is still inaccurate. Why? Because you can’t talk about relative risk reduction and absolute risk reduction unless it’s a randomized control trial.

Dr. Mike Hansen, MD
Internal Medicine | Pulmonary Disease | Critical Care Medicine

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