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PLoS One. 2017 Sep 21;12(9):e0184606. doi: 10.1371/journal.pone.0184606. eCollection 2017.

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

Author information

1
Pulmonary and Critical Care Medicine, Department of Medicine, Marsico Lung Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina United States of America.
2
Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
3
Marsico Lung Institute/Cystic Fibrosis Research Center, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina United States of America.
4
Department of Medicine, Columbia University Medical Center, New York, New York, United States of America.
5
Center for Genomics and Personalized Medicine Research, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States of America.
6
Collaborative Studies Coordinating Center, Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
7
David Geffen School of Medicine, University of California, Los Angeles, California, United States of America.
8
Division of Pulmonary and Critical Care Medicine, University of Michigan Health System, Ann Arbor, Michigan, United States of America.
9
Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
10
Department of Thoracic Medicine and Surgery, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America.
11
Division of Pulmonary and Critical Care Medicine, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
12
Department of Medicine, Weill Cornell Medical College, New York-Presbyterian Hospital/Weill Cornell Medical Center, New York, New York, United States of America.
13
Division of Pulmonary and Critical Care Medicine, University of Nebraska, Omaha, Nebraska, United States of America.
14
Division of Pulmonary, Critical Care, Sleep and Allergy, Department of Medicine and Cardiovascular Research Institute, University of California San Francisco, School of Medicine, San Francisco, California, United States of America.
15
Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine and Department of Veterans Affairs Medical Center, University of Utah, Salt Lake City, Utah, United States of America.
16
Division of Pulmonary and Critical Care Medicine, University of Michigan Health System, Ann Arbor, Michigan; VA Ann Arbor Healthcare System, Ann Arbor, Michigan, United States of America.

Abstract

RATIONALE:

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.

OBJECTIVES:

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.

METHODS:

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.

RESULTS:

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.

CONCLUSIONS:

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.

PMID:
28934249
PMCID:
PMC5608200
DOI:
10.1371/journal.pone.0184606
[Indexed for MEDLINE]
Free PMC Article

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