The minimal important difference of the constant work rate cycle test in severe COPD

Marieke C van der Molen; Dirk-Jan Slebos; Sonja W S Augustijn; Huib A M Kerstjens; Jorine E Hartman

doi:10.1016/j.rmed.2023.107265

The minimal important difference of the constant work rate cycle test in severe COPD

Respir Med. 2023 Aug-Sep:215:107265. doi: 10.1016/j.rmed.2023.107265. Epub 2023 May 22.

Authors

Marieke C van der Molen¹, Dirk-Jan Slebos², Sonja W S Augustijn³, Huib A M Kerstjens², Jorine E Hartman²

Affiliations

¹ University of Groningen, University Medical Center Groningen, Department of Pulmonary Diseases, Groningen, the Netherlands; University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD, Groningen, the Netherlands. Electronic address: m.c.van.der.molen@umcg.nl.
² University of Groningen, University Medical Center Groningen, Department of Pulmonary Diseases, Groningen, the Netherlands; University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD, Groningen, the Netherlands.
³ University of Groningen, University Medical Center Groningen, Department of Pulmonary Diseases, Groningen, the Netherlands.

PMID: 37224889
DOI: 10.1016/j.rmed.2023.107265

Abstract

Background: The Constant Work Rate Cycle Test (CWRT) is a commonly used and sensitive test to detect treatment success in patients with Chronic Obstructive Pulmonary Disease (COPD). Earlier, the Minimal Important Difference (MID) of the CWRT was estimated at 101 s (or 34%) change from baseline based on one well executed study. However, this study was performed in a population of patients with mild-to-moderate COPD, and we have learned that MIDs might be quite different in patients with severe COPD. Therefore, we aimed to establish the MID of the CWRT in patients with severe COPD.

Methods: We included 141 patients with severe COPD, who underwent either pulmonary rehabilitation, bronchoscopic lung volume reduction with endobronchial valves, or a sham bronchoscopy as a control group. CWRT workload was set at 75% of the peak work capacity, as determined by an incremental cycle test. We used the change in 6-min walking test (6-MWT), forced expiratory volume in 1s (FEV₁), residual volume (RV), and St. George's Respiratory Questionnaire (SGRQ) total score as anchors to calculate the MID.

Results: All anchors had an association of ≥0.41 with change in CWRT. The MID estimates for the different anchors were: 6-MWT 278 s (95%), FEV₁ 273 s (90%), RV 240 s (84%), and SGRQ 208 s (71%). The average of these four MID estimates resulted in an MID of 250 s (or 85%).

Conclusion: We established the MID for CWRT at 250 s (or 85%) change from baseline in patients with severe COPD.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Forced Expiratory Volume
Humans
Pulmonary Disease, Chronic Obstructive*
Quality of Life
Residual Volume
Respiratory Function Tests / methods
Treatment Outcome