This claim is erroneous on its face. In framing its guideline, NICE did not “
create a new definition” of ME/CFS. It worked with the definition formulated by the Institute of Medicine (now the US National Academy of Medicine) which dates back to
2015. This is the definition that the
US Centers for Disease Control uses when providing information to healthcare providers. In other words, the definition here is not “new”. It is well established and widely employed.
With regard to logic, using the IOM definition did not “
automatically downgrade the certainty of trial evidence.” This is because the “certainty of trial evidence” was already of an inherently low grade, having been reliant on
self-report data gathered using non-blinded methods. In other words, the trial evidence suffered because so many researchers conducted
sloppy research. Focusing on subjective measures of so-called “recovery” — and overlooking objective ones — represents extremely poor research practice.