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

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.

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.

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).

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