The results of clinical trials are making their way to publication showing hydroxychloroquine to be effective in many, although possibly not all, situations. The American media is silent on these studies. Instead, the American media headline a non-experimental and biased study showing the drug to be ineffective and, even, a cause of death.
The non-experimental study concerns a large number of COVID-19 patients (sample size 368) at Veterans Administration medical centers. These were older men, many with comorbidities. The study is non-experimental because patients weren't randomly assigned to control and experimental groups. Instead, the sicker patients tended to be administered hydroxychloroquine. It is recognized by the authors of this study that the correlation of severity with prescription imparts bias into the sample. The authors reduce (but do not eliminate) this bias through "propensity score adjustment."
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