It's worth reading the entire article for a decent layperson's interpretation of the controversy around this study. Though the sample size is high, the most noteworthy detail for my semi-trained...
It's worth reading the entire article for a decent layperson's interpretation of the controversy around this study.
Though the sample size is high, the most noteworthy detail for my semi-trained eyes is that it's a retrospective study. It's well-established that retrospective studies are highly prone to sources of bias.
Retrospective studies involve looking back through an accumulation of existing data and statistically fitting explanations to it, rather than designing a forward-looking, controlled experiment to test a hypothesis. [There's a good illustration here.] It's easy to inadvertently change the definition of a "needle" when you're searching "haystacks" of records that themselves may not be coded correctly.
In the Henry Ford study, there's at least one known example of this phenomenon - patients were not randomly assigned to treatments. The hydroxychloroquine recipients may have been different in important respects (age, general health, etc.) from patients who didn't receive HCQ. Many of the hydroxychloroquine- or HCQ+azithromycin-treated patients also received immunosuppressive treatments like steroids and tocilizumab, which are now known to be independently effective in reducing COVID-19 mortality. The researchers excluded a significant number of patients not yet released from the hospital, who may still be a significant source of uncounted mortality. While the lead physician touts peer review of the article for publication, journal acceptance doesn't obviate these bases for criticism.
Needless to say, expect a newly widened divergence of public opinion on hydroxychloroquine benefits depending on one's politics and preferred information sources. See also this summary of other evidence concerning hydroxychloroquine's efficacy in COVID-19 treatment and prevention.
It's worth reading the entire article for a decent layperson's interpretation of the controversy around this study.
Though the sample size is high, the most noteworthy detail for my semi-trained eyes is that it's a retrospective study. It's well-established that retrospective studies are highly prone to sources of bias.
Retrospective studies involve looking back through an accumulation of existing data and statistically fitting explanations to it, rather than designing a forward-looking, controlled experiment to test a hypothesis. [There's a good illustration here.] It's easy to inadvertently change the definition of a "needle" when you're searching "haystacks" of records that themselves may not be coded correctly.
In the Henry Ford study, there's at least one known example of this phenomenon - patients were not randomly assigned to treatments. The hydroxychloroquine recipients may have been different in important respects (age, general health, etc.) from patients who didn't receive HCQ. Many of the hydroxychloroquine- or HCQ+azithromycin-treated patients also received immunosuppressive treatments like steroids and tocilizumab, which are now known to be independently effective in reducing COVID-19 mortality. The researchers excluded a significant number of patients not yet released from the hospital, who may still be a significant source of uncounted mortality. While the lead physician touts peer review of the article for publication, journal acceptance doesn't obviate these bases for criticism.
Needless to say, expect a newly widened divergence of public opinion on hydroxychloroquine benefits depending on one's politics and preferred information sources. See also this summary of other evidence concerning hydroxychloroquine's efficacy in COVID-19 treatment and prevention.