where trial participants are included on the basis of their historic diagnosis, and where the study population is large enough to provide statistical power based on sub cohorts defined by the criteria, then at least three out of: Fukuda, ICC, CCC, NICE2021 and IOM2015 should be applied.
or
where researchers are themselves assessing participants against criteria and where the study population is large enough to provide statistical power based on sub cohorts defined by the criteria, then at least Fukuda, NICE2021 and IOM2015 should be applied.