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      The minimal important difference for target lobe volume reduction after endoscopic valve therapy

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          Endoscopic valve therapy aims at target lobe volume reduction (TLVR) that is associated with improved lung function, exercise tolerance and quality of life in emphysema patients. So far, a TLVR of >350 mL was considered to be indicative of a positive response to treatment. However, it is not really known what amount of TLVR is crucial following valve implantation.

          Patients and methods

          TLVR, forced expiratory volume in 1 second (FEV 1), residual volume (RV) and 6-minute walk distance (6-MWD) were assessed before and 3 months after valve implantation in 119 patients. TLVR was calculated based on computed tomography (CT) scan analysis using imaging software (Apollo; VIDA Diagnostics). Minimal important difference estimates were calculated by anchor-based and distribution-based methods.


          Patients treated with valves experienced a mean change of 0.11 L in FEV 1, −0.51 L in RV, 44 m in 6-MWD and a TLVR of 945 mL. Using a linear regression and receiver operating characteristic analysis based on two of three anchors (ΔFEV 1, ΔRV), the estimated minimal important difference for TLVR was between 890 and 1,070 mL (ie, 49%–54% of the baseline TLV).


          In future, a TLVR between 49% and 54% of the baseline TLV, should be used when interpreting the clinical relevance.

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          Most cited references 16

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          A randomized study of endobronchial valves for advanced emphysema.

          Endobronchial valves that allow air to escape from a pulmonary lobe but not enter it can induce a reduction in lobar volume that may thereby improve lung function and exercise tolerance in patients with pulmonary hyperinflation related to advanced emphysema. We compared the safety and efficacy of endobronchial-valve therapy in patients with heterogeneous emphysema versus standard medical care. Efficacy end points were percent changes in the forced expiratory volume in 1 second (FEV1) and the 6-minute walk test on intention-to-treat analysis. We assessed safety on the basis of the rate of a composite of six major complications. Of 321 enrolled patients, 220 were randomly assigned to receive endobronchial valves (EBV group) and 101 to receive standard medical care (control group). At 6 months, there was an increase of 4.3% in the FEV1 in the EBV group (an increase of 1.0 percentage point in the percent of the predicted value), as compared with a decrease of 2.5% in the control group (a decrease of 0.9 percentage point in the percent of the predicted value). Thus, there was a mean between-group difference of 6.8% in the FEV1 (P=0.005). Roughly similar between-group differences were observed for the 6-minute walk test. At 12 months, the rate of the complications composite was 10.3% in the EBV group versus 4.6% in the control group (P=0.17). At 90 days, in the EBV group, as compared with the control group, there were increased rates of exacerbation of chronic obstructive pulmonary disease (COPD) requiring hospitalization (7.9% vs. 1.1%, P=0.03) and hemoptysis (6.1% vs. 0%, P=0.01). The rate of pneumonia in the target lobe in the EBV group was 4.2% at 12 months. Greater radiographic evidence of emphysema heterogeneity and fissure completeness was associated with an enhanced response to treatment. Endobronchial-valve treatment for advanced heterogeneous emphysema induced modest improvements in lung function, exercise tolerance, and symptoms at the cost of more frequent exacerbations of COPD, pneumonia, and hemoptysis after implantation. (Funded by Pulmonx; number, NCT00129584.)
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            The minimal important difference of exercise tests in severe COPD.

             Milo A. Puhan,  Robert Wise,   (2011)
            Our aim was to determine the minimal important difference (MID) for 6-min walk distance (6MWD) and maximal cycle exercise capacity (MCEC) in patients with severe chronic obstructive pulmonary disease (COPD). 1,218 patients enrolled in the National Emphysema Treatment Trial completed exercise tests before and after 4-6 weeks of pre-trial rehabilitation, and 6 months after randomisation to surgery or medical care. The St George's Respiratory Questionnaire (domain and total scores) and University of California San Diego Shortness of Breath Questionnaire (total score) served as anchors for anchor-based MID estimates. In order to calculate distribution-based estimates, we used the standard error of measurement, Cohen's effect size and the empirical rule effect size. Anchor-based estimates for the 6MWD were 18.9 m (95% CI 18.1-20.1 m), 24.2 m (95% CI 23.4-25.4 m), 24.6 m (95% CI 23.4-25.7 m) and 26.4 m (95% CI 25.4-27.4 m), which were similar to distribution-based MID estimates of 25.7, 26.8 and 30.6 m. For MCEC, anchor-based estimates for the MID were 2.2 W (95% CI 2.0-2.4 W), 3.2 W (95% CI 3.0-3.4 W), 3.2 W (95% CI 3.0-3.4 W) and 3.3 W (95% CI 3.0-3.5 W), while distribution-based estimates were 5.3 and 5.5 W. We suggest a MID of 26 ± 2 m for 6MWD and 4 ± 1 W for MCEC for patients with severe COPD.
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              Minimal clinically important differences in COPD lung function.

               James Donohue (2005)
              The FEV1 is widely used by physicians in the diagnosis, staging, treatment, monitoring, and establishing prognosis for patients with COPD. The MCID is the smallest difference which patients perceive as beneficial and which would mandate a change in patient management. A precise MCID for FEV1 has not been established. In attempt to establish a MCID for predose or trough FEV1, several limitations need to be addressed. There are issues such as reproducibility, repeatability, acceptability, variability, placebo effect, and equipment effects. Patient factors, such as baseline level of FEV1, albuterol reversibility, diurnal variation, influence the results. Nonetheless, using anchoring techniques, a change in pre dose FEV1 of about 100 mL can be perceived by patients, correlates with fewer relapses following exacerbations and is in the range usually achieved with bronchodilators approved for COPD. In the future, consistent reporting of spirometric variables, such as a predose FEV1 and other outcomes, can be incorporated into a more quantitative effort to establish the MCID. Also distributional/statistical methods may be useful in determining the MCID FEV1.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                01 February 2018
                : 13
                : 465-472
                [1 ]Pneumology and Critical Care Medicine, Thoraxklinik at University of Heidelberg, Heidelberg
                [2 ]Translational Lung Research Center Heidelberg (TLRCH), German Center for Lung Research, Heidelberg (DZL)
                [3 ]Diagnostic and Interventional Radiology, Thoraxklinik at University of Heidelberg, Heidelberg
                [4 ]Diagnostic and Interventional Radiology at University of Heidelberg, Heidelberg, Germany
                Author notes
                Correspondence: D Gompelmann, Pneumology and Critical Care Medicine, Thoraxklinik at University of Heidelberg, Röntgenstr 1, 69126 Heidelberg, Germany, Email daniela.gompelmann@
                © 2018 Gompelmann 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.

                Original Research

                Respiratory medicine

                emphysema, hyperinflation, target lobe volume reduction


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