Proposal and validation of the minimum clinically important difference in emphysema progression
Ho, Emily S Y Ellis, Paul R Subramanian, Deepak Stockley, Robert A Turner, Alice M
Ho, Emily S Y
Ellis, Paul R
Subramanian, Deepak
Stockley, Robert A
Turner, Alice M
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Affiliation
University of Birmingham; University Hospitals Birmingham NHS Foundation Trust; Sandwell and West Birmingham NHS Trust; University Hospitals of Derby and Burton NHS Foundation Trust
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Publication date
2025-03
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Abstract
Objective: The severity of emphysema may be measured by lung density on computed tomography (CT) scanning, and in alpha-1 antitrypsin deficiency (AATD) this measure has been used as the primary outcome in trials of disease-modifying therapy, namely augmentation. However, the minimum clinically important difference (MCID) in lung density change is not known; this study aimed to derive and validate MCIDs for density values in AATD. Methods: The distribution method and anchoring density against forced expiratory volume in 1 second (FEV1) were used to derive mean and 95% confidence intervals for the MCID. Data from systematic reviews of CT density measurement and therapy for AATD obtained both absolute and annual changes in lung density. Using the range of potential MCID generated by these methods, a value was chosen for validation against mortality, lung function, and health status in the Birmingham, United Kingdom AATD cohort, using regression to adjust for confounders. Results: Anchor and distribution methods generated a probable MCID of -1.87 g/L/year (range -1.53 to -2.20). The greatest differences between groups were found at the -2.2g/L/year with a greater FEV1 decline in individuals with greater lung loss. Absolute lung density change had a probable MCID of -2.04g/L (range -1.83 to -2.30), and there was a difference in lung function (p<0.001) and mortality; where individuals whose absolute lung loss of more than -2.04g/L had a greater risk of death (p<0.05). Interpretation: From initial evidence, we have shown absolute lung density change as a potential outcome for emphysema modifying therapies in AATD rather than annual density change, with an MCID of -2.04g/L.
Citation
Ho ESY, Ellis PR, Kavanagh D, Subramanian D, Stockley RA, Turner AM. Proposal and Validation of the Minimum Clinically Important Difference in Emphysema Progression. Chronic Obstr Pulm Dis. 2025 Mar 27;12(2):109-116. doi: 10.15326/jcopdf.2024.0511
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Article