Posted by Jay Livingston
When Jill Lepore, in an article on police, misreported a percentage from a research study, I said (here), “If a number just doesn’t sound right — it’s way too big or way too small — you’d better double-check.”
On Sunday, FDA commissioner Dr. Stephen M. Hahn cited a Mayo Clinic study showing that blood-plasma treatment for Covid-19 yielded a 35% reduction in mortality. Here’s how Dr. Hahn explained it.
| So let me just put this in perspective. Many of you know I was a cancer doctor before I became FDA commissioner, and a thirty-five percent improvement in survival is a pretty substantial clinical benefit. What that means is . . . 100 people who are sick with Covid-19, thirty-five would have been saved by the administration of plasma. |
Not just pretty substantial, very substantial. So substantial that maybe we should double-check. When we do, this is what we find:
The Mayo Clinic study measured 7-day mortality rates.
- Of patients who did not receive plasma, 11.9% died
- Of patients who did receive plasma, 8.7% died
If you lower something from 11.9 to 8.7, that’s a 35% reduction (11.9 - 8.7 = 3.2. and 3.2 is about 35% of the original rate). Dr. Hahn mistook the reduction in the percent of mortality for a reduction in number of patients who died. For 100 Covid patients, the number of lives saved by plasma would be closer to 3, not 35.
Hahn made his statement at a press conference Sunday night. Trump and HHS secretary Alex Azar were also there and emphasized the 35% figure (see this Bloomberg story). But other scientists who heard about the claim quickly pointed out the error. Within twenty-four hours, Hahn admitted his error, saying in a Tweet, “I have been criticized for remarks I made Sunday night about the benefits of convalescent plasma. The criticism is entirely justified.”
I wonder if President Trump and Secretary Azar will offer similar corrections. No I don’t. Trump keeps promising Covid miracles, so he will continue to tout plasma as a miracle cure along with his other pet miracle cure hydroxy chloroquine and whatever other miracle cures come along until Covid 19 disappears. Like a miracle.
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