Let's think about the comparison group for a moment What can comparing people who received plasma early rather than late actually tell us?
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Firstly, it can't tell us if convalescent plasma works. These people were not randomized, and they are manifestly inadequate as a control to determine if CP has any benefit over treatment as usual
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It's pretty simple - if you give EVERYONE in your study the same treatment, you can't make any inferences about whether it works or not We have to wait for less inherently biased research to be published to have any hope of answering that question
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So what CAN these figures tell us? Well, they can potentially point to whether giving CP early is better than giving it late
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Now, I don't think the published research is adequate to actually make that decision. There are too many confounders, and they aren't well controlled for in the analysis of CP early vs CP late But it's potentially possible that this study COULD tell us that
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If nothing else, it could just be that people who receive CP early are less sick than those who get it late because they didn't delay coming into hospital and so die less anyway Too many confounders to know anything for sure
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So IF convalescent plasma works for COVID-19 - which we still don't know - and IF it's more effective than care as usual, then it MAY be better to give the treatment early as opposed to late That's all the published research can really say!
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End of conversation
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Confounding by indication
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I think 35% is from comparing those receiving low vs high antibody level plasma, RR of 7 day mortality? Does seem like they cherry picked the rosiest number.pic.twitter.com/osCjCCpevi
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