PT  - JOURNAL ARTICLE
AU  - J.E. Hartman
AU  - N.H.T. ten Hacken
AU  - K. Klooster
AU  - H.M. Boezen
AU  - M.H.G. de Greef
AU  - Dirk-Jan Slebos
TI  - The minimal important difference for residual volume in patients with severe emphysema
AID  - 10.1183/09031936.00219111
DP  - 2012 Jan 01
TA  - European Respiratory Journal
PG  - erj02191-2011
4099  - http://erj.ersjournals.com/content/early/2012/03/22/09031936.00219111.short
4100  - http://erj.ersjournals.com/content/early/2012/03/22/09031936.00219111.full
AB  - Residual Volume measured by body plethysmography is a routine measurement in clinical pulmonary practice and is often an important outcome variable in clinical trials. However, it is not known which size of improvement can be regarded as being important in severe emphysema patients. Therefore, the aim of the study is to establish the Minimal Important Difference (MID) for Residual Volume in severe emphysema patients undergoing bronchoscopic lung volume reduction.Ninety-one severe emphysema patients were included. Residual Volume and Total Lung Capacity were measured by body plethysmography. MID estimates were calculated with anchor-based and distribution-based methods. FEV1, Six-Minute-Walk-Distance and SGRQ total score were used as anchors and Cohen's effect size was used as distribution-based method.The calculated MID estimates according to the different anchors and methods ranged between −0.31;−0.43 L for Residual Volume, −6.1;−8.6% for percentage change in Residual Volume from baseline and −2.8;−4.0% for RV%TLC.These MID estimates are useful for sample size determination of new studies on interventions aimed at reducing Residual Volume and for interpreting the results from clinical trials in severe emphysema patients.