Have you ever played that game where, on a semi-sunny day, you lay on the grass eyes skywards and try and fit cloud shapes to objects or people? Y'know 'that cloud looks like a T-Rex dinosaur' or 'that cloud looks like my great Aunt Matilda walking the dog'. Your interpretation might often be shared with your compadres, but more often that not our individual perception and sensation makes others sit-up and question 'Eh?'
Amongst the various descriptions, diagnoses and conditions discussed in this blog, one of the least well defined is that of Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (CFS). Compared for example with autism, which has only two formal diagnostic definitions (ICD and DSM), CFS has at least three descriptions (here - see page 144 onwards) and very possibly more. More importantly that autism, as a defined condition, has a large degree of overlap between DSM and ICD versions (I always wondered why we needed both), whereas the criteria for CFS can be a little more nebulous.
Why is this relevant? Well, in order to provide accurate guesses at the numbers of people presenting with a particular condition at a particular time, you really need to make sure that they are all being 'graded' the same way in terms of definition of their symptoms. Clouds that look like T-Rex dinosaurs need to look like T-Rex dinosaurs to everyone.
An interesting paper* has appeared recently in BMC Medicine by Nacul and colleagues (open-access) on the prevalence of ME/CFS in various regions of England. The minimum prevalence rate was reported as 0.2% for all areas combined, with London showing the highest rate (0.31%) compared with other regions. Researchers however analysed more than just overall prevalence; they analysed trends in the estimated prevalence of ME/CFS based on various criteria used to characterise ME/CFS and found various similarities and differences as a result. The short introduction to the paper on the BMC website describes the paper as suggesting "..a new call to use definitions consistently will make it easier to classify sub-groups of patients according to treatment needs".
This paper and some of its findings struck a chord with me. One of the only times that I have ventured experimentally outside of autism research was when 'attempting' to categorise the symptoms present in ME/CFS in a paper published a few years back. I am not saying that our research was on a par with the latest BMC offering but we, like many other researchers, quickly discovered that CFS/ME is a mighty complex thing to pin down, not helped by having so many different criteria (and indeed overlapping conditions).
Whilst accepting that individuals often (always?) present symptoms differently even within the same condition/diagnosis and symptoms can 'move around' for lots of different reasons, standardisation of applied criteria is a cornerstone of accurate diagnosis. There is an argument that without it, diagnosis of that condition is always open to question and research into that condition is difficult at best as per one of my previous posts on the hunt for biomarkers for autism. I know that there are lots of very passionate public debates on-going in ME/CFS at the moment on various things from XMRV to researcher-abuse which on the whole tend to be as a result of just 'not knowing'. Agreeing on and implementing universal diagnostic criteria might just represent the first steps to tackling some of these issues and progressing research to make a real impact on many people's lives.
I end with an offer to walk the dinosaur with me... anyone, anyone?
* Nacul LC. et al. Prevalence of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) in three regions of England: a repeated cross-sectional study in primary care. BMC Medicine. 2011
Interesting commentary. You are absolutely correct that a universally accepted criteria, or biomarker, would go a long way in improving epidemiology research and reports of prevalence. One problem is that this illness has no butterfly rash or other visible abnormalities. Despite the advancement in human reasoning, physicians and researchers still depend on what they see, either through a microscope or in a physical exam. I have the illness and I have said, "If only my pee were blue."ReplyDelete
While many biological abnormalities can be objectively measured, they have not shown to be in 100% of patients and may also be seen in other conditions.
And that's the conundrum. Until you narrow the criteria, you may be including others that have similar but different illnesses. So, you will not find a biomarker found in all of them. But how do you know you have the right cohort if you don't have a biomarker?
The ME-ICC came out in July and included 26 researchers from 13 countries. Published in the Journal of Internal Medicine, it proposes a criteria that will separate out those who don't actually have the disease.
What is ironic to me, is that as a patient, I can very easily tell if someone has ME/CFS. It's like if you hear someone describe where they grew up. If you grew up in the same town, you will realize it as they describe the same unique features of that town that you are familiar with. The hangout for teenagers, the most hated teachers, the yearly festivals, etc.
That's the way it is with someone with CFS. When I hear they wake up feeling like they have a hangover. When they describe hot flashes, nausea and vomiting when they don't rest after feeling the fatigue. When they mention nickle-size bruises appearing on limbs suddenly. When they describe noise and light sensitivity. When they describe moments of brain fog such that they can't say more than one or two-word responses. When they say they lose things and put things in the wrong place, throw things away without realizing it. Insomnia, vertigo, and that doesn't even go to the blood or brain test abnormalities we share.
While these symptoms are seen in other illnesses, the pattern of having them together is unique to ME/CFS. Even if a person doesn't have all of them, the pattern can still be seen. It is like a fingerprint. When you have nine points matching between two fingerprints, you know it is of the same person.
Thanks for the comments Tina. With my autism research hat on, the same issues with regards to a 'biomarker' pertain there i.e. spectral condition, lots of overlapping symptoms (and co-morbidities, etc, large degree of heterogeneity. I posted about it a few days back: http://questioning-answers.blogspot.com/2011/09/biomarkers-for-autism.htmlReplyDelete
One of the possibilities mentioned in that post is to move away from just symptom presentations as your anchor point for biomarkers and look towards potential markers based on things like responses to treatment and deliniating best and non-responders to see if this might light our way.
I suppose at the end of the day MC/CFS is as complex as everything else; with the additional possibility that there may actually be no universal biomarkers as a result.