Two existing definitions of chronic multisymptom illness (CMI) -- one by the Centers for Disease Control and Prevention and another from a study of Kansas Gulf War veterans -- should be used by the U.S. Department of Veterans Affairs to guide research and treatment of Gulf War veterans, says a new report from the Institute of Medicine. Determining which definition to use in different circumstances should be based on specific needs. Furthermore, the term "Gulf War illness" should replace "chronic multisymptom illness" to reflect the group in which the illness manifests and the group's distinctive experiences, said the committee that wrote the report.
The VA asked IOM to develop a case definition for CMI as it pertains to the veteran population who served during the 1990-1991 Gulf War, as well as recommend appropriate terminology for referring to CMI. Case definitions enable health care providers to prescribe standard treatments and enroll patients into research and drug trials. A case definition might be broad in its reach to recognize all people who have a disease but may inadvertently include some who do not. However, a more specific definition might be too narrow and miss some individuals. Researchers might desire a narrow case definition to assemble a study sample in which all the subjects have a high probability of being afflicted by a certain condition. For physicians, a broader consensus case definition may be preferred to determine appropriate evaluation and treatment.
Since the conflict in the Persian Gulf from 1990 to 1991, Gulf War veterans have experienced various unexplained symptoms that many associate with their service, but no specific exposure has been definitively associated with symptoms. The wide variation in symptoms has complicated efforts to determine whether a distinctive illness exists, as many symptoms of CMI overlap with those of other diseases and conditions, such as fibromyalgia and chronic fatigue syndrome.
The committee found no clinically validated tests or measures for diagnosing CMI and was unable to develop a new consensus definition of CMI given the lack of uniform symptoms, the variety of symptoms, and the long onset and duration. Serious limitations in the methodologies for data collection and the analytic approaches used in many of the studies also undermined the committee's ability to present a single definition.
The committee recommended that the VA use two current definitions -- the CDC and Kansas definitions -- because they capture the most common symptoms and will provide a framework for further treatment and research. The CDC case definition, which has been widely used by researchers, identifies 29 percent to 60 percent of U.S. Gulf War-deployed veterans as CMI cases, depending on the population studied. The Kansas definition identifies 34 percent as CMI cases in the Kansas Gulf War veterans studied. The committee stressed that one definition should not be applied for all purposes, and instead researchers and clinicians should select one based on their needs. The CDC definition is broad and has the greatest concordance with all the other definitions but is less restrictive than the Kansas definition. For example, the CDC definition is effective for identifying as many individuals as possible. It will likely include individuals who do not have CMI, whereas the Kansas definition will likely exclude some cases.
"CMI is an important cause of disability among Gulf War veterans," said Kenneth Shine, chair of the committee and special adviser to the chancellor at the University of Texas System. "The diversity and intensity of exposures and experiences, as well as the breadth and extent of symptoms, warrant workable definitions of the illness and nomenclature so the VA can advance research and administer effective treatments."
The committee acknowledged that the two definitions cover most of the common CMI symptoms, but they do not reflect the complete array reported by Gulf War veterans. Given the lag in time between first reports of CMI and epidemiologic study, lack of exposure monitoring, and the absence of validated laboratory tests, it is not possible to define many of the typical elements associated with a case definition, the committee said. However, the VA should systematically assess existing data to identify additional features of CMI -- such as period of onset, duration, severity, and frequency of symptoms -- to produce a more robust case definition.
The committee also recommended that the VA use the term Gulf War illness rather than chronic multisymptom illness. The terminology associated with the symptoms changed over the years. The term Gulf War syndrome was used initially, but numerous other terms have appeared in medical and scientific literature, including Gulf War illness, unexplained illness, medically unexplained symptoms, medically unexplained physical symptoms, and CMI. Gulf War illness is reflective of both the geographic area and the unique experience of this group of veterans and has been used by many researchers, the committee said.