Reference: Reeves 2005
Evidence Level 1-
A. Study Description
  1. Aim: to apply the 1994 CFS criteria by standardized reproducible criteria.
  2. Environmental or prognostic factor: Diagnosis of CFS: the International CFS Study Group recommendations for diagnosis (including
    1. Medical Outcomes Survey Short Form −36 – SF-36
    2. Checklist Individual Strength or Multidimensional Fatigue Inventory to quantify fatigue
    3. CDC Symptom Inventory for occurrence, duration and severity of symptoms) were applied and compared to diagnosis by the case definition algorithm used in the surveillance study (based on subjective responses to direct questions re fatigue and whether at least 4 case defining symptoms were present).
  3. Comparison (control): see above
  4. Sample size: Cases: CFS 58; ISF (insufficient symptoms of fatigue) 59; CFS + MD (melancholic depression) 27; ISF + MD 28. Controls: 55
  5. Characteristics of the patient population: matched to CFS on sex, race, age and body mass index.
  6. Length of follow up: NA
  7. Outcome measures: illness classification by surveillance criteria and by International CFS Group recommendations (see above).
  8. Source of funding: CDC
B. Internal validity
  1. The study addresses an appropriate and clearly focused question: Yes
  2. Cases and controls taken from comparable populations: Yes
  3. Same exclusion criteria for cases and controls: Yes
  4. Percentage of each group participated: Cases: 83% of CFS;84% of ISF; 66%CSF and MD; 72% ISF and MD. Controls: 55/58
  5. Comparison made between participants and non-participants to establish differences: Yes
  6. Cases clearly defined and differentiated from controls: Yes
  7. Clearly established that controls are non-cases: Yes
  8. Measures taken to prevent knowledge of primary exposure influencing case ascertainment: NA
  9. Exposure status measured in a standard, valid, reliable way: NA
  10. Main confounders identified and taken into account: Yes
C. External validity (Generalisability – see also other sections for details)
  1. Setting: Participants were admitted to a Wichita hospital research unit for two days.
  2. Inclusion criteria: All participants participated in the 4 year Wichita CFS Surveillance Study
  3. Recruitment: All 70 CFS patients from the Surveillance Study were invited; matched controls were selected from healthy study participants; 70 randomly selected ISF patients were asked; all 41 surveillance participants with depression were asked.
  4. Safety issues: none
D. Results/Effect size

Odds ratios not provided (mean standard deviation given). Only 13% of patients who met 1994 surveillance criteria for CFS met those same criteria in this study. 40% fulfilled CFS criteria of the International CFS Study Group using a clinically empirical definition.

Overall, this study aids in the definition and diagnosis of CFS by testing a diagnostic strategy which provides health care providers with objective measures of the disability associated with CFS and which may be less affected by the day to day fluctuation of the illness and, rather reflect the underlying chronic illness process.
E. Quality rating

Study design: Case control

The statistical analysis is not fully described but this study does appear to be of adequate size and careful case control design to represent a relationship between diagnostic category and scores on the empirical measurement tools recommended by the International CFS Study Group

Consistency of results with other studies in the field: Unknown

Directness of comparisons to intervention or patient population of interest in this guideline: Yes

From: Appendix 2, Data extraction tables

Cover of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (or Encephalopathy)
Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (or Encephalopathy): Diagnosis and Management of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (or Encephalopathy) in Adults and Children [Internet].
NICE Clinical Guidelines, No. 53.
National Collaborating Centre for Primary Care (UK).
Copyright © 2007, Royal College of General Practitioners.

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