title: Subclassifying chronic fatigue syndrome through exercise testing.
abstract: OBJECTIVE
  The purpose of this study was to examine physiological responses of persons with chronic fatigue syndrome (CFS) to a graded exercise test.
  
  
  METHODS
  Cardiopulmonary exercise tests were performed on 189 patients diagnosed with CFS. Based on values for peak oxygen consumption, patients were assigned to one of four impairment categories (none, mild, moderate, and severe), using American Medical Association (AMA) guidelines. A one-way MANOVA was used to determine differences between impairment categories for the dependent variables of age, body mass index, percentage of predicted [OV0312]O(2), resting and peak heart rates, resting and peak systolic blood pressure, respiratory quotient (RQ), and rating of perceived exertion.
  
  
  RESULTS
  Significant differences were found between each impairment level for percentage of predicted [OV0312]O(2) and peak heart rate. Peak systolic blood pressure values for the "moderate," and "severe" groups differed significantly from each other and both other groups. The more impaired groups had lower values. The no impairment group had a significantly higher peak RQ than each of the other impairment levels (all P < 0.001). Peak [OV0312]O(2) values were less than predicted for all groups. Compared with the males, the women achieved actual values for peak [OV0312]O(2) that were closer to their predicted values.
  
  
  CONCLUSIONS
  Despite a common diagnosis, the functional capacity of CFS patients varies greatly. Stratifying patients by function allows for a more meaningful interpretation of the responses to exercise and may enable differential diagnosis between subsets of CFS patients.
authors.affiliation: University of the Pacific, Department of Sport Sciences, Stockton, CA 95211, USA. mvanness@uop.edu
authors.forename: J Mark
authors.initials: JM
authors.lastname: Vanness
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Snell
authors.forename: David R
authors.initials: DR
authors.lastname: Strayer
authors.forename: Line
authors.initials: L
authors.lastname: Dempsey
authors.forename: Staci R
authors.initials: SR
authors.lastname: Stevens
mesh_terms: D000328:Adult; D005080:Exercise Test; D015673:Fatigue Syndrome, Chronic / Q000145:classification* / Q000175:diagnosis / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D010809:Physical Fitness; D012016:Reference Values; D012720:Severity of Illness Index