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Diagnosing ME/CFS in the participants

Since this was a self-report study, ME/CFS was diagnosed by responses to the questionnaire. The study contained detailed questions pertaining to both the CDC's 1988 and 1994 case definitions.

In the long-term group 188 subjects met the 1988 case definition of CFS and another 70 met only the broader 1994 definition. 19 short-term subjects met the 1988 case definition and the other 9 met only the 1994 definition.

We also asked about concurrent conditions. So none of the respondents we used in the analyses also had AIDS, multiple sclerosis or systemic lupus erythematosis, for instance. In addition, we asked how they had been diagnosed with ME/CFS. Of the original 287 long-term respondents (a 72% response rate to the questionnaire), 75 patients had been diagnosed with ME/CFS by one of 19 prominent ME/CFS research physicians, 198 by another physician and 12 were self-diagnosed. 29 of these original subjects had to be eliminated from the analysis because missing data or the presence of a contra-indicated condition prevented the applications of both the 1988 and 1994 case definitions.