The Institute of Medicine (IOM) recently released their report regarding a new name (i.e., systemic exertion intolerance disease) and case definition for chronic fatigue syndrome (CFS). In brief, the IOM proposed that at least four symptoms needed to be present to be included in this new case definition: substantial reductions or impairments in the ability to engage in pre-illness levels of occupational, educational, social or personal activities; post-exertional malaise; unrefreshing sleep; and at least one of the two following symptoms: cognitive impairment or orthostatic intolerance.
Melvin Ramsay, the distinguished British physician who helped create the first diagnostic criteria for myalgic encephalomyelitis (ME), also specified four domains within the original ME case definition. However, in 1988, the Centers for Disease Control renamed this illness CFS, and expanded the case definition’s domains to eight. In addition to patient discontent over the name change to CFS, the muddled case definition had a number of problems as it is well known that as unexplained somatic symptoms increase, there is a greater likelihood of identifying individuals who have psychiatric comorbidities.
If there are ambiguities with case definitions, there will be difficulties in replicating findings across different labs, estimating the prevalence of the illness, consistently identifying biomarkers, and determining which treatments help patients. To develop or validate a reliable case definition, we need to provide operationally explicit criteria for a case definition, and develop a consensus within the scientific community on the case definition. The members of the preeminent IOM body are distinguished scientists and clinicians, and many are leaders within the ME and CFS fields.
However, regarding their proposed case definition, there is considerable evidence that cognitive impairment should belong to the group of cardinal and required symptoms. Orthostatic intolerance doesn’t evidence prevalence rates as high as the other proposed core symptoms, nor is there any clear justification of requiring patients to have either cognitive impairment or orthostatic intolerance. (I do not know of any factor analytic study that has separated the symptoms into this particular structure.) There may be different groupings of patients (different features, levels of severity) and this was not adequately addressed. Empirical methods could have been employed to test the proposed classification system. It is unclear why the committee members limited themselves to surveying extant studies rather than testing out their proposed model with an actual data set, particularly as they proposed a specific constellation of symptoms that had not been previously investigated. It was also a mistake to apply identical diagnostic criteria to both children and adults. Finally, there is a clear need to exclude those who have a primary affective psychiatric disorder, as including these patients in the case definition would confound the interpretation of epidemiologic and treatment studies, and complicate efforts to identify biological markers for this illness.
There are steps that could remedy some of the above issues.
First, there are a number of existing data sets that could be used to explore and validate this new diagnostic system. Compare the findings with other case definitions.
Second, there has been considerable discussion among patient groups regarding prominent differences among patients. There is a need for studies to determine whether distinct categories or continuous measures best capture these differences. Employ both large data sets and sophisticated research methods to address such investigations.
Third, due to the secrecy inherent in the IOM committee process, there was a significant breakdown in communicating with other government efforts (such as the ongoing Pathways to Prevention effort), as well as the larger scientific and patient community. The IOM report has a comprehensive section devoted to dissemination activities, indicating that the committee members clearly understood the importance of gaining support from key constituencies and gatekeepers. However, the patient and scientific community could have been actively involved in selecting the case definition and its criteria prior to the dissemination effort. This involvement would represent a departure from the process that has historically existed, and which patient activists have bitterly challenged.
An alternative vision is still possible if those in power are willing to bring all interested parties to the table, including international representatives, historians on the science of illness criteria, and social scientists adept at developing consensus. In a collaborative, open, interactive, and inclusive process, issues may be explored, committees may be charged with making recommendations, and key gatekeepers may work collaboratively and transparently to build a consensus for change. Involve all parties — patients, scientists, clinicians, and government officials — in the decision-making process.
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