Briefing notes on the CDC Empirical Case Definition for CFS
(I spent a lot of time recently searching for a concise overview of the CDC Criteria and couldn’t find one – here’s what I was trying to find out :)
The Centers for Disease Control and Prevention (CDC) ‘s empirical case definition for CFS involves assessment of symptoms, disability, and fatigue through the :
• Symptom Inventory,
• the Medical Outcomes Survey Short-Form-36
• and the Multidimensional Fatigue Inventory . ( Jason et al 2008 )
“Prepared by government bureaucrats, rather than by physicians . “ the CDC case definition according to Dr. Nancy Klimas is “rife with ambiguity. Symptoms are counted either as present or absent, without regard to severity or frequency." http://www.name-us.org/DefintionsPages/DefCFS.htm)
In 1988 after an outbreak at Incline Village Nevada, (Stein 2005) the CDC formed a committee that named the disorder “Chronic Fatigue Syndrome” and suggested criteria for a research definition (Holmes et al, 1988). These criteria were found clinically problematic and in 1994 the CDC revised their definition publishing what is commonly referred to as the “Fukuda criteria” (Fukuda et al, 1994) (Stein 2005), which selects less severely ill patients ; as Margaret Williams points out : the US Centres for Disease Control (CDC) produced yet more “guidelines” for the case definition of “CFS”, this time making sure that all physical signs were removed from the case definition. (“Signs” are observable by doctors, whilst “symptoms” are described by patients). Both Michael Sharpe and Simon Wessely were involved in this 1994 re- definition of “CFS”.
The Fukuda criteria require only one mandatory symptom: disabling fatigue of greater than 6 months duration.
In addition there must be at least 4 of:
• impaired memory/concentration
• sore throat, tender lymph nodes
• muscle pain
• multi-joint pain
• new headache,
• unrefreshing sleep
• post-exertional fatigue.
This definition lacks specificity because common symptoms such as autonomic and endocrine symptoms were not included. (Stein 2005)
The CDC’s earlier definitions (Holmes et al, 1988) and (Fukuda, 1994), both very similar to the Diagnostic and Statistical Manual of Mental Disorder's somatization disorder (The National Forum), have been widely criticised . Betty Dowsett , for example, stated they “ elevated tonsillitis, glandular enlargement and fatigue to unreal importance while overlooking the characteristic encephalitic features of the genuine illness” as well as inflating “ the possibility of a psychiatric diagnosis, leading to the incorporation of such a heterogeneous population of psychiatric and non-psychiatric causes “ that research groups were unable to compare results or evaluate treatment. "(Dowsett B)
The new definition, which “continues more than ever to propagate that ME/CFS abnormalities are theoretical and experimental “,(karinaxx 2010 ) appears to be even more vague than its predecessors . As Ezelius points out : “It is important to note that the new criteria is so much "loosened up" that it encompasses 2,5% of the general population instead of around 0,4% as with the earlier Fukuda definition 1994 criteria.” (Ezelius 2008)
Under the Symptom Inventory, for example, the overall level of symptoms is relatively low for patients with classic ME/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 definition 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.”
Under the Medical Outcomes Survey Short-Form-36 (SF 36) an individual may not have any reduction 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. ( Jason et al 2010).
Under the Multidimensional Fatigue Inventory severe fatigue is defined as greater than or equal to 13 on the MFI general fatigue or greater than or equal to 10 on the reduced activity, which means that it would be possible to meet the fatigue criterion without significant fatigue; i.e. with reduced activity alone. 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 case definition. (Najar, Porter, & Jason, 2007).
In summary “The CDC has made the "CFS" criteria so loose that it eliminates anyone with any neurological signs or symptoms yet ME is a neurological disease.”(The National Forum). The CDC Criteria uses polythetic criteria (i.e., patients are only required to have four out of a possible eight symptoms). Yet two of these eight symptoms (post-exertional malaise and memory/concentration problems) are an essential feature of this illness and the Fukuda et al. criteria do not require that these symptoms be present among all patients.
"In contrast, the Canadian clinical case definition does require specific ME/CFS symptoms such as post-exertional malaise and memory/concentration problems. "(Jason et al 2010)
“The Canadian Criteria include multiple abnormal physical findings such as spatial instability, ataxia, muscle weakness and fasciculation, restless leg syndrome, and tender lymphadenopathy.
All of the exclusionary conditions included in the 1994 CDC Fukuda Criteria for CFS (1) are also listed as exclusions in the 2003 Canadian Consensus Criteria (2). The Canadian definition actually excludes more neurologic (and other medical) conditions than the Fukuda Criteria.
However, the 1994 CDC Fukuda Criteria for CFS specifically does not exclude anxiety disorders, somatoform disorders, nonpsychotic or melancholic depression, or neurasthenia, while the Canadian Consensus Criteria excludes primary psychiatric disorders. The 1994 CDC Fukuda Criteria for CFS also does not exclude “any condition, such as Lyme disease or syphillis, that was treated with definitive therapy before development of chronic symptoms,” while the Canadian Criteria does exclude “infectious diseases such as tuberculosis, chronic hepatitis, Lyme disease, etc.” (ixchelkali 2010)
Ezelius (2010) comments that “for the already heterogeneous CFS-Fukuda set, it would be a benefit if one could exclude the ME-Ramsay (or ME/CFS-Canada) patients from the group, thus making it less heterogeneous. The excluded ME patients shall then form a separate group. “
Finally , it is hugely significant that the CDC itself declares “ that myalgic encephalomyelitis (ME) was defined in the 1950s as being distinct from CFS,” and recognizes “ that there is not a current consensus case definition for ME. “http://livingwithchronicfatiguesyndrome.wordpress.com/2010/09/16/the-cdc-responds/
..such a gift, surely for campaigners ??
Greg Crowhurst Sept 2010
Dowsett B A Rose by Any Other Name http://www.25megroup.org/Information/Medical/dowsett%27s/Rose%20by%20any%20other%20Name.htm
Ezelius 2008 , CFS is no longer CFS, and it was never ME me-cfs.se/dok/081205-cfs-no-longer-cfs.pdf
Jason et al (2008) Evaluating the Centers for Disease Control's Empirical Chronic Fatigue Syndrome Case Definition Journal of DisabilityPolicy Studies Online : http://jdps.sagepub.com
Jason et al (2010) Problems with the New CDC CFS Prevalence Estimateshttp://www.iacfsme.org/IssueswithCDCEmpiricalCaseDefinitionandPrev/tabid/105/Default.aspx
Jason L et al (2010) The Development of a Revised Canadian Myalgic
Encephalomyelitis-Chronic Fatigue Syndrome Case Definition
Karinaxx 2010 XMRV/ME/CFS How do we react to the recent events ? http://www.prohealth.com/me-cfs/blog/boardDetail.cfm?id=1399098
Najar, N., Porter, N., & Jason, L.A. (2007, Jan.). Evaluating the CDC new case definition. Poster presented at the International Association of Chronic Fatigue Syndrome, Ft. Lauderdale, Fl.
Stein E Psychiatric Treatment Guidelines sacfs.asn.au/download/guidelines_psychiatrists.pdf
The National Forum http://www.ncf-net.org/forum/summer-vol11-1.htm
Williams M Notes on the involvement of Wessely et al with the Insurance Industry and how they deal with ME/CFS claims http://www.meactionuk.org.uk/Notes_on_the_Insurance_issue_in_ME.htm