Comparison of distinctive models for calculating an interlobar emphysema heterogeneity index in patients prior to endoscopic lung volume reduction

Abstract

BackgroundThe degree of interlobar emphysema heterogeneity is thought to play an important role in the outcome of endoscopic lung volume reduction (ELVR) therapy of patients with advanced COPD. There are multiple ways one could possibly define interlobar emphysema heterogeneity, and there is no standardized definition.PurposeThe aim of this study was to derive a formula for calculating an interlobar emphysema heterogeneity index (HI) when evaluating a patient for ELVR. Furthermore, an attempt was made to identify a threshold for relevant interlobar emphysema heterogeneity with regard to ELVR.Patients and methodsWe retrospectively analyzed 50 patients who had undergone technically successful ELVR with placement of one-way valves at our institution and had received lung function tests and computed tomography scans before and after treatment. Predictive accuracy of the different methods for HI calculation was assessed with receiver-operating characteristic curve analysis, assuming a minimum difference in forced expiratory volume in 1 second of 100 mL to indicate a clinically important change.ResultsThe HI defined as emphysema score of the targeted lobe (TL) minus emphysema score of the ipsilateral nontargeted lobe disregarding the middle lobe yielded the best predicative accuracy (AUC =0.73, P=0.008). The HI defined as emphysema score of the TL minus emphysema score of the lung without the TL showed a similarly good predictive accuracy (AUC =0.72, P=0.009). Subgroup analysis suggests that the impact of interlobar emphysema heterogeneity is of greater importance in patients with upper lobe predominant emphysema than in patients with lower lobe predominant emphysema.ConclusionThis study reveals the most appropriate ways of calculating an interlobar emphysema heterogeneity with regard to ELVR.

The impact of emphysema heterogeneity on treatment response after endobronchial valve treatment

“…Furthermore, we calculated the heterogeneity index as the difference in destruction between the target and ipsilateral lobe, including the right middle lobe, if applicable. However, there are multiple ways to calculate this index [ 15 ]. Using a different definition for heterogeneity could have resulted in different findings.…”

“…Currently, there is no gold standard to define interlobar emphysema heterogeneity, and multiple approaches are available [ 15 ]. We calculated the heterogeneity index as the difference in destruction (%LAA −950insp ) between the treatment target lobe and the ipsilateral nontargeted lobe, including the right middle lobe.…”

Pulmonary quantitative CT imaging in focal and diffuse disease: current research and clinical applications

“…Regional quantification of emphysema by CT is paramount for the planning of LVR. 70,113 Emphysema distribution pattern and fissures integrity are pivotal for prediction of treatment efficacy.…”

Selecting Patients for Lobar Lung Volume Reduction Therapy: What Quantitative Computed Tomography Parameters Matter?

“…We chose to go by the frequently used attenuation threshold of -950 HU [21 -23]. The interlobar heterogeneity index was in turn calculated from the emphysema scores of adjacent ipsilateral lung lobes as described in the literature [1,24] using the following formula: Heterogeneity index = targeted lobe emphysema scoreipsilateral non-targeted lobe emphysema score disregarding the right middle lobe. An example of a qCT analysis of two different lungs and the resulting parameters are presented in ▶ Fig.…”