title: Psychometric Properties of the Asthma Symptom Diary (ASD), a Diary for Use in Clinical Trials of Persistent Asthma.
abstract: BACKGROUND
  No currently available asthma symptom diary has sufficient validation to be recommended for use as a core asthma outcome measure.
  
  
  OBJECTIVE
  The objective of this study was to provide validation data for the 10-item asthma symptom diary (ASD).
  
  
  METHODS
  Data were collected in a 4-week prospective, observational study. Subjects completed 3 study visits, completing the ASD twice daily at home for 28 days. Psychometric properties in terms of dimensionality, reliability, validity, and responsiveness were assessed.
  
  
  RESULTS
  Data from 276 subjects were analyzed; mean age was 42.9 (standard deviation [SD] = 16.4) years, mean asthma duration was 23.3 (SD = 16.8) years, and 69.6% were female. Confirmatory factor and Rasch analysis supported the ASD as unidimensional and adequately measuring the spectrum of asthma symptom severity. High Cronbach's α (0.94) and intraclass correlation coefficients (0.89-0.95) supported reliability. A high correlation between the 7-day average ASD score and the Asthma Control Questionnaire (ACQ) total score (r = 0.75) and Asthma Quality of Life Questionnaire total scores (r = -0.76), and a moderate correlation with FEV1% predicted (r = -0.30) supported convergent validity. Significant differences (P < .001) between groups classified by ACQ scores supported known-group validity. The 7-day average ASD scores were responsive to change, with significantly higher score changes (P < .001) in responders versus nonresponders. Minimally important differences were calculated and found to be in the range of 0.1-0.3.
  
  
  CONCLUSIONS
  Results of this study indicated that the ASD is a reliable and valid asthma symptom measure for use in adult and adolescent asthma patients to evaluate the effect of treatment on asthma in clinical trials.
authors.affiliation: Amgen Inc., Thousand Oaks, Calif. Electronic address: gglobe@amgen.com.
authors.forename: Gary
authors.initials: G
authors.lastname: Globe
authors.affiliation: Evidera, London, United Kingdom.
authors.forename: Ingela
authors.initials: I
authors.lastname: Wiklund
authors.affiliation: Gilead Sciences, Inc., Foster City, Calif.
authors.forename: Joseph
authors.initials: J
authors.lastname: Lin
authors.affiliation: Evidera, Bethesda, Md.
authors.forename: Wen-Hung
authors.initials: WH
authors.lastname: Chen
authors.affiliation: Health Research Associates, Inc., Mountlake Terrace, Wash.
authors.forename: Mona
authors.initials: M
authors.lastname: Martin
authors.affiliation: Evidera, Bethesda, Md.
authors.forename: Maria S
authors.initials: MS
authors.lastname: Mattera
authors.affiliation: Evidera, London, United Kingdom.
authors.forename: Robyn
authors.initials: R
authors.lastname: von Maltzahn
authors.affiliation: Amgen Inc., Thousand Oaks, Calif.
authors.forename: Jing Yuan
authors.initials: JY
authors.lastname: Feng
authors.affiliation: Amgen Inc., Thousand Oaks, Calif.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chon
authors.affiliation: Amgen Inc., Thousand Oaks, Calif.
authors.forename: Hema N
authors.initials: HN
authors.lastname: Viswanathan
authors.affiliation: Department of Allergy, Kaiser Permanente Medical Center, San Diego, Calif.
authors.forename: Michael
authors.initials: M
authors.lastname: Schatz
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000453:epidemiology; D002908:Chronic Disease; D002986:Clinical Trials as Topic; D005260:Female; D006801:Humans; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D011594:Psychometrics / Q000379:methods*; D015203:Reproducibility of Results; D057566:Self Report; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Asthma; Patient-reported outcome; Psychometrics; Symptoms; Validity