Convalescent plasma fails the parachute test
Convalescent plasma is the new hydroxychloroquine.
After a recent emergency use authorization (EUA) by the FDA, convalescent plasma has been hailed as “a major breakthrough” for COVID, at least by the folks who pressured the FDA to approve it.
So what’s the deal here? News like this almost always brings up more questions than it does answers. Let’s take a look at what convalescent plasma is and the role of this treatment in the management of patients with COVID.
What is convalescent plasma?
Let’s start very basic here. Plasma is a component of blood.
Blood seems homogenous when we look at it, but it’s really a big mixture of a number of different components. Whole blood contains water, proteins, electrolytes, glucose, and different types of cells.
If you take blood and put it into a centrifuge - a huge piece of lab equipment that spins at over 2000 rotations per minute - the different component of blood separate into different layers based on their density.
Plasma is the least dense top layer of the centrifuged blood that contains water, salts, enzymes, and antibodies (among other things).
Plasma has no cells. That means no red blood cells, no white blood cells, and no platelets.
But plasma does contain antibodies, which is why we’re talking about it today.
Why might convalescent plasma be useful in COVID?
Convalescent plasma is the plasma taken from a person who has already had COVID and cleared their infection.
The theory is that by infusing the antibodies from patients who have already beaten the virus, you may provide some protection against COVID infection.
This type of treatment - passively transferring antibodies from a person who already had a disease - has long been considered to be a possible adjunctive treatment strategy for numerous infectious diseases.
Convalescent plasma was a huge part of treatment during the 1918 influenza epidemic, for example.
What does the research on convalescent plasma tell us about it’s effectiveness?
The latest research that’s been touted by the FDA as “proof” of the effectiveness on convalescent plasma should send chills down your spine.
The data on convalescent plasma manages to be simultaneously unimpressive science and disturbing misinformation from what should be a trusted government body.
Let’s look quickly at the latest study:
The latest pre-print that’s been making the rounds looks at infusing convalescent plasma within 3 days of a COVID diagnosis versus after 4 days of a COVID diagnosis
This study found that patients who got plasma early had better survival than those who got it late (8.7% death versus 11.9% death)
Higher levels of antibodies was associated with lower mortality
Any problems with this research?
You can’t measure the effectiveness of a treatment by comparing it to itself!
You’re not allowed to say that convalescent plasma has been proven to be an effective treatment because giving it early seems to be better than giving it late!
You’re not allowed to say that convalsence plasma has been proven to be an effective treatment because looking back on the data seems like more = better!
Until there’s a randomized trial comparing convalescent plasma to placebo, we’re left with guessing whether it works or not.
The FDA and HHS should be ashamed by how they’re reporting the data
Look at this press release from our government.
This is propaganda.
Take a look at this quote:
“The FDA’s emergency authorization for convalescent plasma is a milestone achievement in President Trump’s efforts to save lives from COVID-19,” said Secretary Azar.
And:
Stephen M. Hahn, M.D., FDA Commissioner:
I am committed to releasing safe and potentially helpful treatments for COVID-19 as quickly as possible in order to save lives. We’re encouraged by the early promising data that we’ve seen about convalescent plasma. The data from studies conducted this year shows that plasma from patients who’ve recovered from COVID-19 has the potential to help treat those who are suffering from the effects of getting this terrible virus
The problem here isn’t just what they’re saying - although this is a big problem! - it’s also that these people know better!
They are misrepresenting the quality of this research and this serves to mislead the public!
When you mislead people about the effectiveness of treatments to overhype unimpressive findings, you undermine trust in the scientific method and in medical research.
This insidious misrepresentation has a real long term impact. It isn’t trivial.
Convalescent plasma isn’t a parachute
Very few treatments meet the parachute threshold of not requiring a randomized trial to demonstrate benefit.
A parachute is the type of treatment that doesn’t require any research because the impact of using one is so transparently obvious.
If convalescent plasma were a parachute, the numbers reported in the observational trials would be so obviously game changing that no one would be arguing about their effectiveness.
And you can’t forget that convalescent plasma, like any treatment, has risk. There are real potential side effects of infusing someone else’s plasma into your body - there’s no free lunch in medicine.
I’ve said this over and over again, but the repetition will continue until our understanding improves: the road to hell is paved with biologic plausibility. Without a randomized trial we’re just guessing and putting patients at risk for harm.
As a result, we’re wasting time and money, while simultaneously degrading trust in medical research by overhyping treatments with mediocre evidence behind them.
Thank you for reading! If you’ve been enjoying my newsletter, please subscribe and share on social media!