Prepare for the Polemic.
Months ago, I stumbled across this article in Medical Decision Making called "The Fallacy of a Single Diagnosis" by Don Redelmeier and Eldar Shafir (hereafter R&S). In it they purport to show, using vignettes given to mostly lay people, that people have an intuition that there should be a single diagnosis, which, they claim, is wrong, and they attempt to substantiate this claim using a host of references. I make the following observations and counterclaims:
- R&S did indeed show that their respondents thought that having one virus, such as influenza (or EBV, or GAS pharyngitis), decreases the probability of having COVID simultaneously
- Their respondents are not wrong - having influenza does decrease the probability of a diagnosis of COVID
- R&S's own references show that their respondents were normative in judging a reduced probability of COVID if another respiratory pathogen was known to be present