Variability in objective and subjective measures affects baseline values in studies of patients with COPD

• Published in: PloS one Vol. 12; no. 9; p. e0184606
• Main Authors: Anderson, Wayne H., Ha, Jae Wook, Couper, David J., O’Neal, Wanda K., Barr, R. Graham, Bleecker, Eugene R., Carretta, Elizabeth E., Cooper, Christopher B., Doerschuk, Claire M., Drummond, M Bradley, Han, MeiLan K., Hansel, Nadia N., Kim, Victor, Kleerup, Eric C., Martinez, Fernando J., Rennard, Stephen I., Tashkin, Donald, Woodruff, Prescott G., Paine, Robert, Curtis, Jeffrey L., Kanner, Richard E.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 21.09.2017; Public Library of Science (PLoS)
• Subjects: Adult; Aged; Aged, 80 and over; Asthma; Biology and Life Sciences; Blood; Blood Cell Count; Blood cells; Bronchitis; Care and treatment; CAT scans; Chronic obstructive lung disease; Chronic obstructive pulmonary disease; Cigarette smoking; Cigarettes; Clinical trials; Computed tomography; Correlation coefficient; Correlation coefficients; Critical care; Cystic fibrosis; Demographics; Demography; Development and progression; Diagnosis; Emphysema; Exercise Test; Female; Humans; Internal medicine; Lung diseases; Male; Medical research; Medicine; Medicine and Health Sciences; Middle Aged; Monitoring instruments; Patients; Prospective Studies; Pulmonary Disease, Chronic Obstructive - diagnosis; Pulmonary function tests; Pulmonary functions; Questionnaires; Reproducibility; Reproducibility of Results; Respiratory function; Smoking; Spirometry; Surveys and Questionnaires; Time Factors; Tomography, X-Ray Computed; Variability; Womens health; United States; North Carolina; New York; Los Angeles California; United States > US; California; Ann Arbor Michigan; Michigan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0184606

Understanding the reliability and repeatability of clinical measurements used in the diagnosis, treatment and monitoring of disease progression is of critical importance across all disciplines of clinical practice and in clinical trials to assess therapeutic efficacy and safety. Our goal is to understand normal variability for assessing true changes in health status and to more accurately utilize this data to differentiate disease characteristics and outcomes. Our study is the first study designed entirely to establish the repeatability of a large number of instruments utilized for the clinical assessment of COPD in the same subjects over the same period. We utilized SPIROMICS participants (n = 98) that returned to their clinical center within 6 weeks of their baseline visit to repeat complete baseline assessments. Demographics, spirometry, questionnaires, complete blood cell counts (CBC), medical history, and emphysema status by computerized tomography (CT) imaging were obtained. Pulmonary function tests (PFTs) were highly repeatable (ICC's >0.9) but the 6 minute walk (6MW) was less so (ICC = 0.79). Among questionnaires, the Saint George's Respiratory Questionnaire (SGRQ) was most repeatable. Self-reported clinical features, such as exacerbation history, and features of chronic bronchitis, often produced kappa values <0.6. Reported age at starting smoking and average number of cigarettes smoked were modestly repeatable (kappa = 0.76 and 0.79). Complete blood counts (CBC) variables produced intraclass correlation coefficients (ICC) values between 0.6 and 0.8. PFTs were highly repeatable, while subjective measures and subject recall were more variable. Analyses using features with poor repeatability could lead to misclassification and outcome errors. Hence, care should be taken when interpreting change in clinical features based on measures with low repeatability. Efforts to improve repeatability of key clinical features such as exacerbation history and chronic bronchitis are warranted.