No biomarker exists
At present, there is no reliable biomarker for ME/CFS. Diagnoses of ME/CFS are based on manifesting clinical symptoms and there is high inter-patient variability of more complex symptoms/auxiliary and physiological abnormalities, however, amongst physicians, crucially, the symptom of post-exertional malaise (PEM) is increasingly being recognised as inseparable to the manifestation of the disease.
Diagnosis at present is made using clinical criteria
This makes it both clinically and physiologically distinct from other diseases presenting with the symptom of co-morbid long-lasting (chronic) fatigue. It is therefore crucial that we understand which molecular signature(s) are present in various other diseases presenting with co-morbid chronic fatigue, thereby allowing us to determine which markers and pathway abnormalities are specific to ME/CFS.
Once we begin to find replicable and robust biomarkers that are unique to ME/CFS this will reduce the average 5 year period until diagnosis and help ensure ME/CFS patients do not undergo years of stigmatisation and neglect.
Symptom questionnaires designed to focus on the symptom of post-exertional malaise and to thereby identify its presence and measure the degree of severity have been developed[ref]. Importantly at present ME/CFS diagnostic criteria that mandate the presence of PEM for diagnoses (Canadian Consensus, IOM, ICC) do not capture the severity of PEM, so going forward it will be useful to determine the severity of PEM in ME/CFS.
Affecting up to 20 million people worldwide and affecting more of the population than either Multiple Sclerosis and HIV/AIDS, at present, a diagnosis can only be made based on the exclusion of other diseases.
The average level of physical disability is greater than that of Multiple Sclerosis and Rheumatoid arthritis and despite this, there remains no existence of a universal drug target. Current government-backed funding remains substantially less (£0.4 million per year) than that of Multiple Sclerosis (£2.83 million per year) despite the greater (average) disability. The condition remains an unsolved puzzle to medicine.
At present, there are 5 different diagnostic criteria for ME and CFS.
Internationally both the Canadian Consensus Criteria (CCC)(Carruthers et al., 2003) or the Fukuda(1994) criteria are the most frequent means of diagnosis.
However importantly the Fukuda criteria do not mandate the presence of PEM and therefore the CCC is often the preferred approach to diagnosis by many physicians, as PEM is considered by many as the cardinal symptom of ME/CFS.
Canadian Consensus Criteria*
Key symptoms must be present for at least a duration of 6 months and include:
AND at least one symptom from two of the following 3 categories: