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      Minimal Clinically Important Differences for Patient-Reported Outcome Measures of Cough and Sputum in Patients with COPD

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          Cough and sputum are highly prevalent in patients with chronic obstructive pulmonary disease (COPD). Pulmonary rehabilitation (PR) has shown to be effective in managing these symptoms. However, the interpretation of the magnitude of PR effects is hindered by the lack of minimal clinically important differences (MCIDs).


          This study established MCIDs for the Leicester cough questionnaire (LCQ) and the cough and sputum assessment questionnaire (CASA-Q), in patients with COPD after PR.

          Patients and Methods

          An observational prospective study was conducted in patients with COPD who participated in a 12-weeks community-based PR program. Anchor- (mean change, receiver operating characteristic curves and linear regression analysis) and distribution-based methods [0.5*standard deviation; standard error of measurement (SEM); 1.96*SEM; minimal detectable change and effect size] were used to compute the MCIDs. The anchors used were: i) patients and physiotherapists global rating of change scale, ii) COPD assessment test, iii) St. George’s respiratory questionnaire and iv) occurrence of an exacerbation during PR. Pooled MCIDs were computed using the arithmetic weighted mean (2/3 for anchor- and 1/3 for distribution-based methods).


          Forty-nine patients with COPD (81.6% male, 69.8±7.4years, FEV 150.4±19.4 %predicted) were used in the analysis. The pooled MCIDs were 1.3 for LCQ and for CASA-Q domains were: 10.6 - cough symptoms; 10.1 - cough impact; 9.5 - sputum symptoms and 7.8 - sputum impact.


          The MCIDs found in this study are potential estimates to interpret PR effects on cough and sputum, and may contribute to guide interventions.

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          Most cited references 45

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          Measurement of health status. Ascertaining the minimal clinically important difference.

          In recent years quality of life instruments have been featured as primary outcomes in many randomized trials. One of the challenges facing the investigator using such measures is determining the significance of any differences observed, and communicating that significance to clinicians who will be applying the trial results. We have developed an approach to elucidating the significance of changes in score in quality of life instruments by comparing them to global ratings of change. Using this approach we have established a plausible range within which the minimal clinically important difference (MCID) falls. In three studies in which instruments measuring dyspnea, fatigue, and emotional function in patients with chronic heart and lung disease were applied the MCID was represented by mean change in score of approximately 0.5 per item, when responses were presented on a seven point Likert scale. Furthermore, we have established ranges for changes in questionnaire scores that correspond to moderate and large changes in the domains of interest. This information will be useful in interpreting questionnaire scores, both in individuals and in groups of patients participating in controlled trials, and in the planning of new trials.
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            Individual-patient monitoring in clinical practice: are available health status surveys adequate?

            Interest has increased in recent years in incorporating health status measures into clinical practice for use at the individual-patient level. We propose six measurement standards for individual-patient applications: (1) practical features, (2) breadth of health measured, (3) depth of health measured, (4) precision for cross-sectional assessment, (5) precision for longitudinal monitoring and (6) validity. We evaluate five health status surveys (Functional Status Questionnaire, Dartmouth COOP Poster Charts, Nottingham Health Profile, Duke Health Profile, and SF-36 Health Survey) that have been proposed for use in clinical practice. We conducted an analytical literature review to evaluate the six measurement standards for individual-patient applications across the five surveys. The most problematic feature of the five surveys was their lack of precision for individual-patient applications. Across all scales, reliability standards for individual assessment and monitoring were not satisfied, and the 95% CIs were very wide. There was little evidence of the validity of the five surveys for screening, diagnosing, or monitoring individual patients. The health status surveys examined in this paper may not be suitable for monitoring the health and treatment status of individual patients. Clinical usefulness of existing measures might be demonstrated as clinical experience is broadened. At this time, however, it seems that new instruments, or adaptation of existing measures and scaling methods, are needed for individual-patient assessment and monitoring.
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              Pulmonary rehabilitation for chronic obstructive pulmonary disease.

              Widespread application of pulmonary rehabilitation (also known as respiratory rehabilitation) in chronic obstructive pulmonary disease (COPD) should be preceded by demonstrable improvements in function (health-related quality of life, functional and maximal exercise capacity) attributable to the programmes. This review updates the review reported in 2006.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of Chronic Obstructive Pulmonary Disease
                29 January 2020
                : 15
                : 201-212
                [1 ]Respiratory Research and Rehabilitation Laboratory (Lab3R), School of Health Sciences, University of Aveiro (ESSUA) , Aveiro, Portugal
                [2 ]Institute of Biomedicine, School of Health Sciences (iBiMED), University of Aveiro (ESSUA) , Aveiro, Portugal
                [3 ]Pulmonology Department, Centro Hospitalar Do Baixo Vouga (CHBV) , Aveiro, Portugal
                Author notes
                Correspondence: Alda Marques Escola Superior de Saúde, Universidade de Aveiro - Edifício 30 , Agras do Crasto - Campus Universitário de Santiago, Aveiro3810-193, Portugal Email
                © 2020 Rebelo et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (

                Page count
                Figures: 4, Tables: 3, References: 69, Pages: 12
                Original Research


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