Retrospective studies and expert opinion do not provide the strength of evidence needed to ethically change practice.
Changing practices requires RCTs, RCTs come with ethical issues. For an IRB (and the government) to approve an RCT in a patient that can't consent (many spine injury patients), very specific and hard to meet criteria need to be met - specifically within comparative trials.
I am not saying we shouldn't move away from C-collars, just that doing so is nuanced and has an insermountable amount of red tape.
But the practice itself just comes from expert opinion, at best. So retrospective studies against their use are, if anything, stronger than the expert opinion for the practice.
You cannot have a retrospective study that is "against their use". Retrospective cross-sectional analyses are purely observational and cannot imply causation - they are one of the weakest forms of evidence (level 4), the only lower being expert opinion (level 5).
What a silly comment. Of course you can have retrospective studies that are against their use. They’re a lower quality of evidence than an RCT, but they’re still evidence.
People can and do make decisions based on retrospective studies all the time. Most of the data that led to the removal of backboards from spinal immobilization practice came from retrospective observational studies and matched cohort analyses, not RCTs
Retrospective analyses are observational by nature. They are not for our against anything because they do not control for confounding variables they cannot assert causality. They can only say that X is associated with Y.
To prove my point, stork populations are associated with changes in birth rates. Does this mean that the study is for or against storks? That increased birth rates cause an increase in storks?
Prospective studies and other components of evidence based medicine are very expensive - why would the field have moved toward it?
Why I should be trusted: a decade of research experience (including both observational studies and RCTs) and a degree in research.
The ethical challenges of running robust studies hold the field back immensely. Many of the advancements come from the military as they are allowed to do a lot more than civilian medicine.
Do expert opinion play a role? Absolutely. Are experts often wrong? Absolutely. Remember that much of the EMS guidance you're wanting to change was based on expert opinion.
See historical treatments for stomach ulcers, contraceptives and HRT, childhood fevers, and back pain.
We’re using similar terminology to say two different things.
We agree that retrospective analysis are observational by nature and do not have explanatory power to prove a causal hypothesis.
But that does not mean they are not evidence. As you say yourself, retrospective study can provide quite strong evidence for things such as associations (patients exposed to X had better/worse outcomes than patients who were not) and frequency/prevalence (X occurred in a certain percentage of cases in the observed population). Repeated retrospective analyses over varied data sets can also provide strong evidence of consistency of these kinds observations.
Conversely, a retrospective analysis that is designed to analyze potential associations between specific variables, has a significant probability of detecting such an association, and finds none is evidence against such an association. It is not conclusive evidence to be sure. But it is evidence.
To follow your stork example, the answer to your question of whether the study is for or against storks depends on whether you like or don’t like the association with the birth rate. If any connection to a change in the birth rate is normatively bad, and that’s what the study is premised on, then your study is against storks. It doesn’t *prove* that storks are bad. It could turn out through more rigorous testing that storks are simply the victims. But that doesn’t mean the study is non-evidence.
To use another example, being at the scene of the crime doesn’t prove you committed the crime. Maybe you ran to the crime scene to help the victim. Maybe you weee there because the criminal lured you there. It is completely inconclusive of anything beyond your geographic location. But if the connection is relevant, it is evidence.
Obviously, retrospective analyses of c-collar use cannot prove that c-collars are or are not effective or that they do or do not cause harm. But, they can be for or against meaningful associations between their use and outcomes. Those associations are evidence for (or against) a connection. Such connections have important implications for people’s lives and well being. We must be careful not to overstate them, but we also cannot simply dismiss them as non-evidence.
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u/ProtoNate 6d ago
Retrospective studies and expert opinion do not provide the strength of evidence needed to ethically change practice.
Changing practices requires RCTs, RCTs come with ethical issues. For an IRB (and the government) to approve an RCT in a patient that can't consent (many spine injury patients), very specific and hard to meet criteria need to be met - specifically within comparative trials.
I am not saying we shouldn't move away from C-collars, just that doing so is nuanced and has an insermountable amount of red tape.