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

Abstract

Objective

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 (FEV₁), 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.

Results

Patients treated with valves experienced a mean change of 0.11 L in FEV₁, −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 (ΔFEV₁, ΔRV), the estimated minimal important difference for TLVR was between 890 and 1,070 mL (ie, 49%–54% of the baseline TLV).

Conclusion

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

Keywords:

• emphysema
• hyperinflation
• target lobe volume reduction

Disclosure

DG obtained lecture and travel fees from Pulmonx, Olympus, Chiesi, Boehringer Ingelheim, Novartis, Astra Zeneca, Munidpharma, Berlin Chemie and Grifols. MS obtained fees for lectures and advisory boards from the following companies: Olympus, Pulmonx, Astra Zeneca, Novartis, Teva, GSK, PneumRx and Boston Scientific. RE obtained lecture and travel fees from Olympus, Pulmonx and Uptake Medical. CPH has stock ownership in medical industry: Stada, GSK; Patents: Method and Device for Representing the Microstructure of the Lungs. IPC8 Class: AA61B5055FI, PAN: 20080208038, Inventors: W Schreiber, U Wolf, AW Scholz and CP Heussel; consultation or other fees from Schering-Plough (2009, 2010), Pfizer (2008–2014), Basilea (2008–2010), Boehringer Ingelheim (2010–2014), Novartis (2010 and 2012), Roche (2010), Astellas (2011 and 2012), Gilead (2011–2014), MSD (2011–2013), Lilly (2011), Intermune (2013 and 2014) and Fresenius (2013 and 2014); expert testimony no; research funding from Siemens (2012–2014), Pfizer (2012–2014), MeVis (2012 and 2013) and Boehringer Ingelheim (2015); lecture fees from Gilead (2008–2014), Essex (2008–2010), Schering-Plough (2008–2010), AstraZeneca (2008–2012), Lilly (2008, 2009 and 2012), Roche (2008 and 2009), MSD (2009–2014), Pfizer (2010–2014), Bracco (2010 and 2011), MEDA Pharma (2011), Intermune (2011–2014), Chiesi (2012), Siemens (2012), Covidien (2012), Pierre Fabre (2012), Boehringer Ingelheim (2012–2014), Grifols (2012) and Novartis (2013 and 2014). FH obtained fees for lectures and advisory boards from Astra, Allmirall, Berlin Chemie, Boehringer, Roche, GSK, Pulmonx, BTG, Olypmus, PneumRx, Boston Scientific, Medupdate, Grifols, CSL Behring, Omniamed, Lilly, Novartis, Teva and Uptake and Vital Air. The authors report no other conflicts of interest in this work.