Evaluation of the psychometric properties of the Nighttime Symptoms of COPD Instrument

• Published in: International journal of chronic obstructive pulmonary disease Vol. 10; no. Issue 1; pp. 475 - 487
• Main Authors: Mocarski, Michelle, Zaiser, Erica, Trundell, Dylan, Make, Barry J, Hareendran, Asha
• Format: Journal Article
• Language: English
• Published: New Zealand Dove Medical Press Limited 01.01.2015; Dove Medical Press Ltd; Dove Medical Press
• Subjects: Adult; Aged; Aged, 80 and over; Analysis; Bronchodilator Agents - therapeutic use; Chronic obstructive pulmonary disease; Circadian Rhythm; Clinical trials; Clinical Trials, Phase III as Topic; Complications and side effects; Diagnosis; Diaries; Dyspnea; Factor Analysis, Statistical; Female; Health aspects; Humans; Lung diseases, Obstructive; Male; Medical tests; Middle Aged; Original Research; Patients; Predictive Value of Tests; Product development; Psychometrics; Pulmonary Disease, Chronic Obstructive - complications; Pulmonary Disease, Chronic Obstructive - diagnosis; Pulmonary Disease, Chronic Obstructive - drug therapy; Pulmonary Disease, Chronic Obstructive - physiopathology; Pulmonary Disease, Chronic Obstructive - psychology; Qualitative research; Quality of Life; Quantitative psychology; Randomized Controlled Trials as Topic; Reproducibility of Results; Severity of Illness Index; Sleep; Sleep disorders; Spirometry; Surveys and Questionnaires; Time Factors; psychometric validation; PRO; nighttime symptoms; COPD
• ISSN: 1178-2005; 1176-9106; 1178-2005
• DOI: 10.2147/COPD.S75776

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. 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. 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. 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.