title: Psychometric properties of the Dutch Chronic Fatigue Syndrome--Activities and Participation Questionnaire (CFS-APQ).
abstract: OBJECTIVE
  The Chronic Fatigue Syndrome-Activities and Participation Questionnaire (CFS-APQ) is a recently developed disease-specific assessment tool for monitoring activity limitations and participation restrictions in patients with chronic fatigue syndrome (CFS). In this study, the convergent validity, content validity, and test-retest reliability of data obtained with the Dutch-language version of the questionnaire were examined.
  
  
  METHODS
  One hundred eleven consecutive patients with CFS were enrolled, of whom 47 fulfilled all inclusion criteria. The subjects were first asked to rate their pain, fatigue, and ability to concentrate using 3 visual analog scales, to list at least 5 activities that had become difficult to perform due to their complaints, and to complete the CFS-APQ. Furthermore, subjects were asked to complete a modified version of the CFS-APQ at home and return it to the investigators. The content of the questionnaire was reviewed using the World Health Organization's International Classification of Impairments, Disability and Health (ICIDH) beta II draft. Spearman rank correlation coefficients (R) were used for the convergent validity analysis, and intraclass correlation coefficients were computed for the assessment of the test-retest data.
  
  
  RESULTS
  Overall scores on the CFS-APQ correlated with the scores from the visual analog scales for pain (R=.51, P<.001) and fatigue (R=.50, P<.001). The majority of the responses (157 out of 183 answers [85.8%]) to the request to "list difficult activities" matched the content of the CFS-APQ. Using the ICIDH beta II draft, 21 out of 26 questions were found to address activities, and the remaining 5 questions measured the participation level. The Cronbach alpha coefficient was.94, and intraclass correlation coefficients for test-retest reliability of the overall scores were >or= .95 (P<.001).
  
  
  CONCLUSIONS
  The results substantiate the convergent validity, content validity, and reliability of the CFS-APQ scores for patients with CFS.
authors.affiliation: Department of Human Physiology, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Belgium. Jo.Nijs@vub.ac.be
authors.forename: Jo
authors.initials: J
authors.lastname: Nijs
authors.forename: Peter
authors.initials: P
authors.lastname: Vaes
authors.forename: Neil
authors.initials: N
authors.lastname: McGregor
authors.forename: Elke
authors.initials: E
authors.lastname: Van Hoof
authors.forename: Kenny
authors.initials: K
authors.lastname: De Meirleir
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D001288:Attention / Q000145:classification; D017281:Cost of Illness; D005221:Fatigue / Q000145:classification; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis*; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D010146:Pain / Q000145:classification; D010147:Pain Measurement; D011594:Psychometrics / Q000295:instrumentation*; D015203:Reproducibility of Results; D013223:Statistics as Topic / Q000379:methods; D011795:Surveys and Questionnaires