I looked at the cohort characteristics a bit more. 100% of ME patients met the IOM criteria, 82% met the Fukuda Criteria and only 53% met the Canadian Consensus Criteria.
Fatigue is necessary in all criteria. Now the discussion becomes a bit more involved because PEM is a necessary symptom in the IOM criteria as well (it’s not necessary for Fukuda).
Now after a post-infectious onset the only criteria that have to met in the Canadian Consensus Criteria are (the illness duration of at least 6 months has automatically been met by all patients in this study):
- Fatigue
- PEM*
- Two or more Neurological / Cognitive Manifestations from a list of symptoms
- At Least One Symptom From Two of the Following Three Categories (autonomic, neuroendocrine, immune) from a list of symptoms
The
IMO criteria furthermore requires patients to either have orthostatic intolerance or cognitive impairment. Since none of the patients in this study seemed to have orthostatic intolerance, this means they have all had to have had cognitive impairment (I will look at the study data at a later time point to see if this can actually be verified by their data when they assessed subjective cognitive impairment).
So where do the 47% come from that don’t meet the Candian Consensus Criteria? The most logical explanation would be that they don’t have at least one symptom in at least 2 categories from the list of symptoms in the autonomic, neuroendocrine, immune list of symptoms in the CCC (I'm working under the additional assumption that people with cognitive impairment in the IMO criteria will have at least 2 cognitive symptoms in the CCC list). There's a caviat* to this mentioned below.
Fukuda is of course extremely vague. It requires fatigue and at least 4 symptoms from the following list: substantial impairment in short-term memory or concentration, sore throat, tender lymph nodes, muscle pain, multi-joint pain without swelling or redness, headaches of a new type/pattern/ severity, unrefreshing sleep, post-exertional malaise lasting more than 24 hours.
Since allegedly all patients had PEM (with the caviat * mentioned below) and cognitive impairment (assuming it aligns with "substantial impairment in short-term memory or concentration") as well as unrefreshing sleep are also a necessary symptom of the IMO criteria this automatically means that 18% of patients didn’t have another symptom of the above list (i.e. 18% didn't have a concurrent occurrence of any of the following symptoms: sore throat, tender lymph nodes, muscle pain, multi-joint pain without swelling or redness, headaches of a new type/pattern/ severity).
*The caviat to this discussion is PEM. The IMO criteria aren’t specific to what PEM exactly is or how long it should last, so some subtle differences could arise there when applying different criteria in the above discussion, it’s not necessary in Fukuda but has to last more than 24 hours to count as one of the symptoms and in the CCC there should be a pathologically slow recovery period – usually 24 hours or longer. It should be noted that in none of the above criteria is a delayed onset necessary.
A whole different question would be who actually assessed these patients and what is their rigor and background. Someone that uses the CCC might be far more rigorous and might not classify something as PEM, whilst others do. Apart from the fact that patients couldn't be sick for longer than 5 years and had to have an infectious onset, I cannot understand how you start off with over 400 patients and only end up studying 8 patients that meet the CCC. Do you have some more details on how the recruitment and assessment worked
@B_V ?
Edited: I'd also like to know which out of the 4/17 patients that recovered met which criteria. That could be revealing.