A lot of information has been circulating recently that hydroxychloroquine, a drug used to treat and prevent malaria, may be effective in treating COVID-19. Is it true? To answer this question, you first need to understand how science works.
The basis of the scientific method is a randomized controlled trial (RCT), easier – experiment. How do we conduct the experiment? We take a sample, for example, 1000 people, randomly assign 500 people to the study intervention and 500 to the control group. The intervention group received hydroxychloroquine and the control group received a placebo. We then analyze whether the intervention group differs from the control group. If there is a big difference, then it can be concluded that the intervention (in in this case via hydroxychloroquine) has little effect.
In the absence of experimental data, scientists usually start by analyzing observational data. Of course, the problem with surveillance studies is that they do not allow direct judgment of causality, but only correlations. Correlation (association) can be useful for the further direction of scientific research. For example, if studies show that hydroxychloroquine correlates with better COVID-19 outcomes (eg, mild symptoms or less mortality), then there may be a causal relationship. But we cannot conclude with certainty from the correlation alone whether hydroxychloroquine is an effective treatment for COVID-19.
Hydroxychloroquine led to higher heart rate and liver side effects
Here are two examples of why correlation doesn’t mean causation.
First example: the data shows that there is a positive correlation between how many people eat ice cream and how many people drown. Does this mean that ice cream leads to more people drowning? The simple answer is that there is a third factor that causes this correlation – external temperature. People eat more ice cream on warm days, and people swim more, and thus drown more on warm days. Yes, in this example, there is a positive correlation between consuming ice cream and drowning, but there really is no causal relationship between consuming ice cream and drowning.
Second example: the data show that there is a positive correlation between how often people visit a doctor and mortality. Does this mean that doctors are killing people? The answer in this case is the problem of biased self-selection. (Self-selection). People who are sick tend to see a doctor much more often, and these people are also more likely to die. Yes, in this example there is a positive correlation between how often people visit a doctor and mortality, but in reality the actual causation is negative – doctors save lives (by at least good doctors).
Now back to hydroxychloroquine and COVID-19. There is a study published on July 1, 2020, which uses data from 2,541 hospitalized patients with COVID-19… Research shows there is a correlation between hydroxychloroquine and COVID-19. This is a good first step. We can even hypothesize that «hydroxychloroquine may be an effective treatment for COVID-19. ” But remember, this is just a correlation based on observational data, not a causal relationship.
In fact, the researchers themselves point out this: “The disadvantage of our study is that it is retrospective and not randomized.” They also note: “Our results need further confirmation from randomized controlled trials that clearly assess the safety and efficacy of hydroxychloroquine for the treatment of COVID-19.” That is, this study found a positive correlation and formed a causal hypothesis that should be tested using RCT.
The good news is that several RCTs have already been made and their results published. An RCT study published July 23, 2020 found no benefit from 667 patients hydroxychloroquine for mild to moderate COVID-19 patients… In another RCT study published July 16, 2020 with 491 Patients, Again Not Finding Benefits of Hydroxychloroquine in Early Stage COVID-19… Another RCT study of 2314 patients, which has already done but not yet published… Again, this study had no effect of hydroxychloroquine on COVID-19 results.
In this study, not only did hydroxychloroquine not improve the results of COVID-19, but it also resulted in a higher heart rate and liver side effects.
As a result, based on existing randomized controlled trials, hydroxychloroquine is not an effective treatment for COVID-19.
Text published with permission of the author
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