Sunday, June 10, 2007

Problems with the New CDC CFS Prevalence Estimates

Leonard Jason, Ph.D., DePaul University

By the early to mid 1990s, the general consensus was that CFS was a relatively rare disorder affecting primarily white, middle-class women. Prevalence estimates of this illness from the CDC ranged from .002% to .0073% (Gunn et al., 1993) suggesting that there were less than 20,000 individuals in the U.S. with this illness. Toward the late 1990s, Jason, Richman and colleagues (1999) used more rigorous community-based samples and found that approximately .42% of the sample was determined to have CFS, or approximately 800,000 people from the US (Jason, Richman et al., 1999). These overall prevalence estimates were later corroborated by the CDC in another community-based sample (Reyes et al., 2003 estimated the CFS prevalence to be .24%).

In Great Britain, community estimates of CFS rates were estimated to be 2.6% (or 2.6 cases among every 100 people; Wessely et al., 1997). One needs to examine a broadened CFS case definition to understand these CFS rates in Great Britain, and if these rates were applied to the US, there would be about 4 million people in the US with CFS. Wessely et al. (1997) indicated that of the 2.6% with CFS, psychological disorders were absent in only .5%. Individuals diagnosed with CFS in this epidemiologic study were subsequently compared to a sample of people with CFS who had been diagnosed from a hospital unit (Euba, Chalder, Deale & Wessely, 1995). Of the community sample, 59% felt their illness might be due to psychological or psychosocial causes compared to 7% for the hospital sample. In Wessely et al.'s (1996) community based sample, only 64% had sleep disturbances and 63% had postexertional malaise. These percentages are rather low, as both symptoms are critical features of CFS. Thes e findings might provide a clue as to why Wessely and colleagues found CFS prevalence rates that were appreciably higher than those found by a second generation of CFS epidemiologic studies in the United States (Jason et al., 1999; Reyes et al., 2003).

It is of interest that the Great Britain CFS rates are within the range of several mood disorders. Mood disorders are the most prevalent psychiatric disorders after anxiety disorders: for major depressive episode, the one-month prevalence is 2.2%, and lifetime prevalence is 5.8% (Regier et al., 1988). Major Depressive Disorder is an example of a primary psychiatric disorder, which has some overlapping symptoms with CFS. Fatigue, sleep disturbances and poor concentration occur in both depression and CFS. Some patients with Major Depressive Disorder also have chronic fatigue and other symptoms that can occur with depression (e.g., unrefreshing sleep, joint pain, muscle pain, impairment in concentration). Fatigue and these four symptoms also are defining criteria for CFS, based on the Fukuda et al. (1994) criteria. It is possible that some patients with a primary affective disorder could be misdiagnosed as having CFS. While fatigue is the principal feature of CFS, fatigue does not assume equal prominence in depression (Friedberg & Jason, 1998; Komaroff et al., 1996). Several CFS symptoms, including prolonged fatigue after physical exertion, night sweats, sore throats, and swollen lymph nodes, are not commonly found in depression. Moreover, illness onset with CFS is often sudden, occurring over a few hours or days, whereas primary depression generally shows a more gradual onset. Some individuals with CFS might have had psychiatric problems before and/or after CFS onset and yet, other individuals may only have primary psychiatric disorders with prominent somatic features. Including the latter type of patients in the current CFS case definition could confound the interpretation of epidemiologic and treatment studies.

The CDC has recently released findings from a community-based epidemiologic study that occurred in Georgia (Reeves, Jones, Maloney, Heim, Hoaglin, Boneva, Morrissey, & Devlin, 2007). While the prior CFS prevalence rate was estimated to be .24% in Wichita, Kansas (Reyes et al., 2003), their new estimated prevalence rates were reported to be considerably higher with 2.54% (remarkably similar to the 2.6% rate in Great Britain, Wessely et al., 1997). The CDC now estimates that six to ten times more people have this illness than their previous reports in the US. In this study, the authors screened for persons who reported fatigue, problems with memory/concentration, unrefreshing sleep or pain rather than simply focusing on the single symptom of fatigue, and the authors indicated that these criteria increased the identified cases by 13%. In addition, the authors used what they referred to as standardized criteria to identify cases, and below we evaluate this new empirical CDC case def inition of CFS. To meet the new CFS criteria, individuals need to meet criteria on symptoms, level of disability and degree of fatigue, and each of these areas is described below.

As one part of the standardized CDC criteria, the Symptom Inventory is used to operationalize the symptoms of CFS (Wagner et al., 2005). For each of 8 critical Fukuda et al. definitional symptoms, patients are asked to rate the symptom on perceived frequency (1 = a little of the time; 2 = some of the time; 3 = most of the time; 4 = all of the time) and severity or intensity of symptoms (the ratings were transformed to the following scale: 1 = mild, 2.5 = moderate, 4 = severe). The frequency and severity scores were multiplied, and the sums for the 8 critical Fukuda et al. (1994) symptoms were summed. Even with summed scores for the empirical case definition needing to be greater or equal to 25 (Reeves et al., 2005), the overall level of symptoms seems relatively low for patients with classic CFS symptoms (the criterion would be met if an individual rated only 2 symptoms as occurring all the time, and one was of moderate and the other of severe severity). In addition, the 8 case def inition symptoms were based on a time period comprising the last month compared to what is specified in the Fukuda et al. (1994) criteria, which states that: "There needs to be the concurrent occurrence of 4 or more of the following symptoms, and all must be persistent or recurrent during 6 or more months of the illness and not predate the fatigue." This change in the case definition has the potential of including more individuals.

Also, part of this new CDC empirical CFS criteria is the use of the Medical Outcomes Survey Short Form-36 (SF-36) to assess substantial reductions in occupational, educational, social or recreational activities. Using the SF-36, these criteria were defined as scores lower that the 25th percentile on the physical function, role physical function, social function, or role emotional. Because the individual only needs to meet one of these areas to meet the CFS criteria, the individual might not have any reductions in key areas of physical functioning, and only impairment in role emotional areas (e.g., problems with work or other daily activities as a result of emotional problems), and then the person could meet disability criteria for CFS. Ware, Snow, and Kosinsi (2000) found that mean for role emotional for a clinical depression group was 38.9,indicating that almost all those with clinical depression would meet criteria for being within the lower 25th percentile on this scale (whic h was a score of less than or equal to 66.7). In Peter White's Dec. 3. 2006 review ( of Reeves et al.'s (2007) article, he states: The use of physical function, role physical and social function sub-scales is consistent with the International Study criteria for CFS, which states that the illness "results in substantial reduction in previous levels of occupational, educational, social, or personal activities." (Reeves et al, 2003). The use of role emotional is not, since it specifically asks about change in function "as a result of any emotional problems". And later White states that "In order to make these important criteria consistent with other studies, I think the authors need to re-analyse their data, omitting this sub-scale."

The last instrument used with the new CDC empirical CFS criteria is the Multidimensional Fatigue Inventory (MFI) (Smets, Garssen, Bonke, & DeHaes, 1995). Severe fatigue was defined as greater than or equal to 13 on the MFI general fatigue or greater than or equal to 10 on the reduced activity. In Peter White's Dec. 3, 2006 review of the Reeves et al.'s (2007) article (, he wrote: "This means that it would be possible to meet the fatigue criterion without significant fatigue; i.e. with reduced activity alone. This is inconsistent with the international study criteria for CFS." In support of this criticism by White, I believe that the general activity items refer to issues that a person with depression might easily endorse. If a person indicated that the following two items were entirely true: "I get little done", "I think I do very little in a day"; they would meet the fatigue criterion for the new CDC empirical cas e definition. Our group is currently studying individuals with major depressive disorder versus those with CFS, and we are finding individuals with a purely affective disorder being classified as having CFS with this new empirical case definition (Najar, Porter, & Jason, 2007).

It is important to better understand the two CDC community based studies (Reyes et al., 2003; Reeves et al., 2007), and this is particularly important as their CFS estimated prevalence rates have changed so dramatically. Of the individuals who were identified as having CFS during the first study (Reyes et al., 2003) that occurred over a three year period (1997 through 2000), 58 were brought back for a two day inpatient study that occurred from December 2002 to July 2003, and only 16 (28% of the original group diagnosed with CFS) had a current consistent diagnosis of CFS, using traditional methods of making this diagnosis. When these investigators employed an empirically derived system (that was used in deriving the higher prevalence rates of 2.54% in the Georgia community based study), 43 rather than 16 individuals who had been traditionally diagnosed as having CFS met this new system. Clearly, this newly developed empirical system brings in many additional people to a CFS diagnosi s. It is very possible that this new empirical classification does identify a group of individuals with high levels of fatigue, impairment, and symptoms, but it might also be identifying a group with high chronic distress and illness, rather than CFS as a unique disorder.

It is at least possible that the 2.54% to 2.6% CFS rates both the United States and Great Britain are due to a broadening of the case definition and possible inclusion of cases with primary psychiatric conditions. Some CFS investigators would not see this as a confounding problem because they believe that high rates of psychiatric comorbidity indicate that CFS is mainly a psychiatric disorder (Abbey, 1993). CFS and depression are two distinct disorders, however, even if they share a number of common symptoms. Most importantly, the erroneous inclusion of people with primary psychiatric conditions in CFS samples will have detrimental consequences for the interpretation of both epidemiologic and treatment efficacy findings.

Reeves et al. (2005) claims that the empirical definition identifies people with CFS in a more precise manner than can occur in the more traditional way. It is primarily the use of this new empirical case definition that has lead to the increase in CFS prevalence rates in the United States. In their use of the empirical case definition, several changes occurred to what had been previously recommended by an international expert committee (Reeves et al., 2003) of recommendations for the case definition of Fukuda et al. (1994). First, rather than excluding those with depressive disorder with melancholic features, only those with a current condition were excluded as opposed to what had been recommended. Of interest, of those 16 within the Reyes et al. (2003) study who had been classified with CFS using the more traditional methods, 6 had a past history of major depressive disorder with melancholic features (Reeves et al., 2005); and it is unclear how many of those 43 who were diagnos ed using the empiric case definition had past depressive disorder with melancholic features. These individuals should have been excluded, and by including them, the broadening of the case definition has the potential to bring into the CFS category those with a primary psychiatric condition. More importantly, there was little agreement between the empirical method of classifying individuals with the more traditional method of comparing whether an individual met the case definition on their critical symptoms. Rather than assuming that this might be a problem with the CFS empirical case definition, they concluded that the more traditional way of diagnosing patients was flawed. As an example of this problem, one individual who was classified as being in remission for CFS using the traditional method was diagnosed with current CFS using the CDC's empirical approach.

Papers are now appearing in the literature using this empirical case definition of CFS, and many have received considerable media attention. For example, Heim et al. (2006) recently used this new empiric case definition and the Wichita study to explore the influence of early adverse experience on risk for developing CFS. The authors concluded that childhood trauma is an important risk factor for CFS. In fact, among those with CFS, 62.8% had some type of early abuse. This is in contrast to findings reported by Taylor and Jason (2002) who found prevalence rates of sexual and physical abuse history among individuals with CFS were comparable with those found in individuals with other conditions involving chronic fatigue, including medically based conditions. Relative to those with CFS who report such history, most individuals with CFS did not report histories of interpersonal abuse.

The Reeves et al. (2005) article clearly used instruments (such as the SF-36) to make diagnostic decisions, rather than encompassing more specific criteria involving aspects of the illness (for example, whether with rest, all symptoms disappear). Given the high variability in symptom severity among persons with fatigue, standardized procedures should be employed for determining whether or not a particular symptom is severe enough to qualify as one of the symptoms required for the diagnosis of fatigue. But one needs to be extremely careful about deciding whether standardized instruments and scores need to include contextual issues, and often they do not. For example, if a patient endorses a symptom such as post-exertional malaise, standardized questions should include duration, frequency, and severity of the symptom including onset, pattern, intensity, and associated factors (see Hawk et al. 2007). Clinical judgment, which has been used in most past studies to diagnoses CFS, remain s an important role even for diseases like lupus, which use a combination of clinical judgment, patient report, and objective measures to come up with a diagnosis. This currently is not occurring with the CFS empirical case definition developed by the CDC.

Some researchers have posited that FMS, CFS, and IBS can be considered functional somatic syndromes (Barsky & Borus, 1999). Functional somatic syndromes are characterized by diffuse, poorly-defined symptoms that cause significant subjective distress and disability, cannot be corroborated by consistent documentation of organic pathology, and are highly prevalent even in healthy, non-patient groups (Barsky & Borus, 1999). Accurate measurement and classification of CFS, FMS and IBS is imperative when evaluating the diagnostic validity of controversial disease entities alternatively labeled, 'functional somatic syndromes'. For example, results of a study by Taylor, Jason and Schoeny (2001) provided support for distinctions between the five conditions of FMS, CFS, somatic depression, somatic anxiety, and IBS, but this will only occur when using symptom criteria that matches actual diagnostic criteria for these illnesses. Measurement that fails to capture the unique characteristics of th ese illnesses might inaccurately conclude that only distress and unwellness characterize these illnesses, thus inappropriately supporting a unitary hypothetical construct called functional somatic syndromes. Ultimately, using a broad or narrow definition of CFS will have important influences on CFS epidemiologic findings, on rates of psychiatric comorbidity, and ultimately on the likelihood of finding biological markers.


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From the One Click Group

From The One Click Group:

Professor Leonard Jason on CFS

Reeves of the CDC.

Professor Leonard Jason writes: "Measurement that fails to capture the unique characteristics of these illnesses might inaccurately conclude that only distress and unwellness characterize these illnesses, thus inappropriately supporting a unitary hypothetical construct called functional somatic syndromes."

One Click comments: "Are the glaring flaws in this CFS study carried out by William Reeves of the CDC et al either research fraud or the deliberate and cynical use of flawed and disreputable information garnering and analysis techniques guaranteed to provide a beneficial psychiatric outcome? It should be noted that psychiatrist Peter White, team leader of the scientifically fraudulent PACE trial that is squandering over £11.1m of British taxpayer's money for psychiatry industry benefit alone, is a close associate of CDC/William Reeves and sits on many CDC committees. This Reeves et al paper represents a disreputable and unethical attempt to falsely conflate somatoform disorder figures to garner further psychiatric funding."


* * *

This has, in fact, been one of the big problems in CFS research.

In the mid-1980s, CDC painted the problem as psychological, sweeping under the rug all the biological facts that were already known to the doctors who were treating the epidemic. The book "Osler’s Web", thanks to research that included the government’s own documents, suggests that there was an ulterior motive in calling it psychological. AIDS had just appeared on the scene and neither CDC nor disability insurance carriers wanted another incurable virus so soon after that one.

Having stated in no uncertain terms that the patients were merely crazy, CDC has had to continue touting that theory so they won’t have to admit they made a mistake, and has structured their efforts to "find a cure" in ways that ensured they would not find any support for a biological cause – nearly two decades ago, Elaine DeFreitas found a retrovirus in CFS patients, CDC could not duplicate her research finding, and upon investigating, she found they were freezing the samples, which she had specifically told them not to do because it would kill the virus. The conclusion of a seasoned researcher was "they didn’t WANT to find anything."

Reeves, whose passion is "stress", was hand-picked to supervise CFS because of his bias that it’s caused by stress, not by a virus. Time and again, he has either completely ignored evidence or twisted it to imply it says what he wants it to say. Even at CDC’s own press conference last year announcing "the first biological evidence" of CFS, he managed to convey to the journalists that the whole problem was stress ... something which is proven inaccurate by 4000+ studies (according to Dr. Komaroff’s count, putting to lie CDC’s assertion that this was the first-ever biological evidence).

To believe Reeves’ version, you’d have to believe that I dealt successfully with the deaths of close family members and dear friends, and the stress of combining full-time work with being a full-time student, but years later, something as simple as cooking dinner (the last thing I did before getting sick) pushed me over the edge and turned me into a psychological basket case.

If coming home from my grandmother’s funeral to the news of my uncle’s death and hearing on the radio before my eyes were open the next morning that two friends (one since kindergarten, the other even longer) had been killed in a DUI accident didn’t push me over the edge as too much emotional stress in too short a time period, then, believe me, a simple day-to-day stressor like having to shop for groceries during the post-work crush or run for the bus wasn’t going to do it, either.

There was no extraordinary stress in my life at the time I got sick; in fact, my stress level was lower than it had been in years. I trace my CFS back to a severe virus with 105 fever; the day before that, I was perfectly healthy, and ever since, I’ve been hitting on four cylinders. Reeves can deny it all he likes, but I was there, I saw it. My boss saw it. The person who cared for me during the virus can describe in detail what he saw, and it wasn’t someone bursting into tears and screaming in an emotional meltdown: he noted objective signs of physical illness like vomiting, diarrhea and a 105 fever. Things that the "psychologizers" like Reeves would like to erase from his and my memory banks and replace instead with a false memory of a major emotional crisis to explain away the inconvenience of my insistence that what I have is biological in origin, triggered by a virus.

Unfortunately, there are those who believe that if they didn’t see it, it didn’t happen. (I’ve had doctors tell me that because I’m not throwing up at 2:30 PM in their office, I also don’t throw up at 7 AM every morning like clockwork; they know better than I do what happens in the privacy of my own home. Thankfully, my current doctor asked the right questions and figured out why "first thing in the morning, before I eat anything" made sense.)

Over the years, CDC has whittled away at the definition of CFS. Where the doctors treating it noted there was always an infectious onset reported by patients, that has been removed from CDC’s definition, which allows for a gradual onset (i.e., bringing patients with slowly worsening psychological problems into the circle). The hallmark symptom of CFS, exercise intolerance, is not in CDC’s definition – the easiest and cheapest way to differentiate between depression and CFS is to send the patient out to exercise and see if they return uplifted or physically collapsed.

There have been some concerns in the patient/activist community, voiced by the physicians and psychiatrists who are patients, that CDC’s patient selection for CFS studies is not selecting patients with CFS, but a large number of patients with psychologically-based fatigue, in order to prove Reeves’ pre-determined answer: that CFS is related to depression or stress or being a fragile female, rather than – as other scientists have proven, biologically linked to MS and polio.

That sort of "research" benefits no one, except Reeves’ ego, by ensuring that his erroneous theory will not be proven wrong.

Patients who didn’t even know they were sick until CDC enrolled them in the CFS study are not indicative of most patients with CFS. We know we’re sick, and often have engaged in a prolonged battle with doctors who think that if a few blood tests are normal, then there’s "nothing wrong", and therefore no necessity for the expensive sleep study, brain scans and neurological testing that would show something very wrong.

When I went for a clinical trial of sleeping pills and reported sleeping an average of 2 hours a night for several years, the doctor supervising the study couldn’t believe that no one had done a sleep study to determine why – it would have proved that I was tossing and turning in pain till 5 AM and disproved the doctors' "nothing wrong" theory.  Like CDC, refusing to verify what the patients actually report as major problems is the easiest way to support psychological theories.

The only difference between the doctor supervising the clinicaltrial and my PCP was that one believed me when I said I wasn’t sleeping well because of untreated pain, and the other turned things around in his mind till he found an explanation he liked better, regardless if that explanation matched the facts he’d been given.

That’s also the only difference between CFS experts and CDC doctors: one group believes patient reports of medical history and symptoms, and the other group dismisses what the patients experience to substitute their own version of the facts, regardless if those facts accurately reflect what patients have told them.