> Though this sounds counterintuitive, it’s the “gold standard” because, if you don’t do this, you leave yourself open to bias
Isn’t there just as much chance for bias if the treatment is voluntary? Maybe the people who are more likely to have health issues are less likely to treat them.
I think there is a valid question about how effective a colonoscopy is given that you get one, and a separate valid question about how effective telling people to get colonoscopies is. According to the article, this paper answer the second question strongly via “gold standard”, and the first question less strongly via secondary analysis.
Part of the reason it’s counterintuitive here is the title of the article is “effect of colonoscopy screening”, not “effect of a doctor’s invitation to have a colonoscopy screening”. The title more than suggests that we’re comparing the outcomes of actually having the screening to not having one.
> maybe the people who don’t have the time/inclination to do one would be better served by an alternative test.
I see what you’re saying - the overall effectiveness of our current system may be low because of a low rate of voluntary adoption of the colonoscopy is low, and even a lower accuracy screen could be more effective if more people opt in.
One problem with drawing a conclusion this way is it ignores the possibility for dramatic changes in either opinion or in procedure of colonoscopies. What if we had the tech to do the colonoscopy at home in private? Would that change the voluntary rate of testing dramatically?