title: Evaluation of the psychometric properties of the Nighttime Symptoms of COPD Instrument.
abstract: BACKGROUND
  Nighttime symptoms can negatively impact the quality of life of patients with chronic obstructive pulmonary disease (COPD). The Nighttime Symptoms of COPD Instrument (NiSCI) was designed to measure the occurrence and severity of nighttime symptoms in patients with COPD, the impact of symptoms on nighttime awakenings, and rescue medication use. The objective of this study was to explore item reduction, inform scoring recommendations, and evaluate the psychometric properties of the NiSCI.
  
  
  METHODS
  COPD patients participating in a Phase III clinical trial completed the NiSCI daily. Item analyses were conducted using weekly mean and single day scores. Descriptive statistics (including percentage of respondents at floor/ceiling and inter-item correlations), factor analyses, and Rasch model analyses were conducted to examine item performance and scoring. Test-retest reliability was assessed for the final instrument using the intraclass correlation coefficient (ICC). Correlations with assessments conducted during study visits were used to evaluate convergent and known-groups validity.
  
  
  RESULTS
  Data from 1,663 COPD patients aged 40-93 years were analyzed. Item analyses supported the generation of four scores. A one-factor structure was confirmed with factor analysis and Rasch analysis for the symptom severity score. Test-retest reliability was confirmed for the six-item symptom severity (ICC, 0.85), number of nighttime awakenings (ICC, 0.82), and rescue medication (ICC, 0.68) scores. Convergent validity was supported by significant correlations between the NiSCI, St George's Respiratory Questionnaire, and Exacerbations of Chronic Obstructive Pulmonary Disease Tool-Respiratory Symptoms scores.
  
  
  CONCLUSIONS
  The results suggest that the NiSCI can be used to determine the severity of nighttime COPD symptoms, the number of nighttime awakenings due to COPD symptoms, and the nighttime use of rescue medication. The NiSCI is a reliable and valid instrument to evaluate these concepts in COPD patients in clinical trials and clinical practice. Scoring recommendations and steps for further research are discussed.
authors.affiliation: Forest Research Institute, Inc., an affiliate of Actavis, Inc., Jersey City, NJ, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Mocarski
authors.affiliation: Evidera, London, UK.
authors.forename: Erica
authors.initials: E
authors.lastname: Zaiser
authors.affiliation: Evidera, London, UK.
authors.forename: Dylan
authors.initials: D
authors.lastname: Trundell
authors.affiliation: National Jewish Health, Denver, CO, USA.
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Make
authors.affiliation: Evidera, London, UK.
authors.forename: Asha
authors.initials: A
authors.lastname: Hareendran
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001993:Bronchodilator Agents / Q000627:therapeutic use; D002940:Circadian Rhythm; D017326:Clinical Trials, Phase III as Topic; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011594:Psychometrics; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology / Q000523:psychology; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D012890:Sleep; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D001993:Bronchodilator Agents
keywords: COPD; PRO; nighttime symptoms; psychometric validation
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