Reading Tea Leaves
In a report issued on March 12, the IOM panel tasked with creating a new case definition for Gulf War Illness declined to do so. This is the first time the IOM was attempting to create a disease case definition, and many ME/CFS advocates (myself included) awaited the report with much trepidation because of the clues it might hold for how the ME/CFS case definition effort would turn out. It didn’t take long for ME/CFS advocates to weigh in (see posts by Jeannette Burmeister, the CFIDS Association, and Cort Johnson). I take no comfort in this report, but I also don’t believe we are automatically doomed.
What the GWI Panel Did
The panel was tasked with reviewing the published literature and holding discussions with researchers and clinicians in order to create a new case definition for GWI (referred to as chronic multisymptom illness in the report and by the Veterans Administration) and to make a recommendation regarding the illness name. They reviewed the case definition and population studies conducted on Gulf War veterans, the largest of which included more than 19,000 subjects. They considered the published data on the symptoms and exposures reported by both deployed and non-deployed Gulf War era veterans, looking for data to support the key elements of a case definition. And they came to a startling conclusion.
The panel said they could not create a new case definition. Why? Because there isn’t enough data, or at least not enough of the right kind of data. The key paragraph is on page 96:
After a thorough discussion of that literature, the committee concluded that it was not feasible to develop a new evidence-based definition of CMI. The case-definition studies do not all consistently identify period of onset, duration, frequency, severity, exposure, exclusionary criteria, or a uniform set of symptoms. There are no clinically validated tests or measures for diagnosing CMI. Furthermore, the symptoms of CMI are not unique to Gulf War-deployed veterans although they occur in the deployed at a higher frequency and with greater severity than in nondeployed era veterans or those deployed elsewhere. . . . Thus, the committee has concluded that the available evidence is insufficient to develop a new case definition of CMI inasmuch as the data are lacking for key elements of a case definition of a symptom-defined condition, which might include, for example, onset, duration, and measures of severity.
The panel went on to identify two case definitions (CDC and Kansas) that captured the common set of symptoms identified in all the case definition studies. The CDC definition is broader because it requires fewer symptoms than the Kansas definition, and does not identify exclusionary conditions. However, the panel said that “neither definition has been sufficiently validated.” The panel recommended that the VA systematically assess the data to see if it could identify some of those missing case definition elements, and that the term CMI be replaced by “Gulf War illness.”
Speaking of ME/CFS
Perhaps it’s not surprising, given the presence of both Dr. Fred Friedberg and Dr. Suzanne Vernon on the panel, that ME/CFS is briefly discussed in the report (see pp. 26-27). The committee notes that multiple ME/CFS case definitions are in use, although without acknowledging the debate over whether it is one illness or many. After pointing out that ME/CFS diagnosis is based on patient-reported symptoms (like CMI), the committee says that the either-or debate over whether ME/CFS is a physical or mental health disorder is not useful. The report states, “The distinction between mental and physical disorders is often arbitrary, and most patients’ experiences of any illness are influenced by biologic, psychologic, and social factors.”
This is not exactly an unequivocal rejection of the psychogenic theory of GWI or ME/CFS. Personally, I am disturbed by what appears to be a change in tactics for the psychosocial school. This topic needs separate discussion, so I’ve addressed it in more detail in my post Changing Tactics.
So what does this GWI report tell us about what to expect from the ME/CFS IOM study? The short answer is “not much,” but I see some cause for concern.
What bothers me about this report is that the panel felt the evidence base was insufficient to create a new case definition, and it makes me wonder about our own evidence base. It is true that GWI appear to have arisen at a specific point in time (Gulf War deployment), while ME/CFS is constantly occurring. But there are similarities between the two evidence bases, too.
First, the panel noted an important limitation of the GWI cohort studies: most of them relied on self-reporting of symptoms on questionnaires (p. 34). This potentially introduces reporting bias and recall bias. Many of the ME/CFS case definition studies rely on self-report through questionnaires, too. Our studies are much much smaller than Gulf War studies, too, weakening the evidence base even further.
Second, the panel concluded that the statistical studies reviewed in Chapter 4 (pp. 67-86) “failed to identify a cluster of people that presented with a unique syndrome.” Instead, the studies found that Gulf War veterans had more symptoms with greater severity than veterans who were not deployed to the Gulf, but that the nondeployed still reported similar symptoms. It seems to me that we may be at risk for a similar conclusion, since at least some studies have found high rates of occurrence of ME/CFS symptoms in control subjects.
Third, I was struck by the similarity between some CMI/GWI case definitions and the core symptoms of ME/CFS. For example, the CDC definition (co-authored by Fukuda in 1998, oddly enough) requires one or more symptoms from at least two of three categories: fatigue, mood/cognition, and musculoskeletal. Does this sound familiar to anyone?! There is no onset requirement, meaning that those symptoms could occur at any time in order to qualify. It seems to me that many, if not all, ME/CFS patients would meet this definition too.
Fourth, post-exertional malaise might occur in GWI. Appendix B of the report presents a combined summary of symptoms reported by veterans in the studies discussed in Chapter 3. Fatigue was reported by a median of more than 30% by Gulf War veterans. The fatigue category includes reports of “fatigue lasting 24h after exertion . . . problems with fatigue lasting more than 24 hours after having made a physical effort” (p. 116). Depending on how one defines and measures post-exertional malaise, these results could be interpreted to fit that term. ME/CFS patients experience more than fatigue after exertion; we suffer from an exacerbation of all symptoms (including immune symptoms), and “fatigue” is a completely inadequate word to describe the prostration and collapse. But will the IOM panel realize that? I think many researchers, even those working in the field, may perceive that PEM is a fatigue experience. If PEM is equated to fatigue lasting more than 24 hours after exertion – which is reported by Gulf War veterans – the argument that post-exertional malaise is unique to ME/CFS falls apart.
Finally, the report notes the elements of a symptom-based case definition, including “period of onset, duration, frequency, severity, exposure, exclusionary criteria, or a uniform set of symptoms.” Because these elements were not consistently identified (or identified at all) in the Gulf War studies, the panel could not create a new case definition. The same inconsistency appears in ME/CFS literature. Differences in onset, duration, frequency/severity, exclusionary criteria and core symptoms are found among the case definition and population studies for ME/CFS – especially if you begin by lumping CFS, ME and ME/CFS studies together.
Some advocates are optimistic about the ME/CFS IOM panel, citing differences in the committee charge, panel composition, and inclusion of unpublished data. But I think I’ve shown that some of the deficiencies in the GWI evidence base could be applied to the ME/CFS evidence base as well.
For me, it comes down to the panel. The ME/CFS IOM panel could decide that the weaknesses in the evidence base are not as problematic, and create a definition based on what we know. We have the benefit of eight panelists who are personally and/or professional acquainted with ME/CFS, a significant improvement over the lack of GWI experts on the other panel. We simply do not know how they will view the evidence, and how effectively they will advocate with the non-ME/CFS experts.
As much as I would like to share in the optimistic confidence of some ME/CFS advocates, I don’t draw solace from the GWI report. But I also can’t conclude that we’re completely screwed. We have a different panel with a different charge. Ultimately, drawing conclusions from the GWI report is an exercise in reading tea leaves – a rather poor way of predicting the future.