CT-based validation of the ESI index for the assessment of emphysema by spirometry

The advanced clinical experimentation of the ESI theory was performed using dedicated math software in cooperation with the Section of Respiratory Medicine directed by Prof. Massimo Pistolesi, Department of Experimental and Clinical Medicine, University of Florence, on a dataset of two hundred consecutive COPD patients who underwent High Resolution Computed Tomography CT scan and spirometry.

The study showed that CT metrics reflecting the severity of emphysema correlated more strongly with ESI (Emphysema Severity Index)  than FEV1 and FEV1/FVC. Furthermore ESI was more independent from functional non- emphysematous gas trapping than standard obstruction indexes.

For validation details and info please read the following paper (Respiratory Research, 2019):

Spirometric assessment of emphysema presence and severity as measured by quantitative CT and CT-based radiomics in COPD


The current version of the ESI-test calculator is based on a novel real-time implementation of the theoretical ESI algorithm. This software was especially designed for clinical practice, pharmacologic trials, medical education and for the evaluation of emphysema whenever spirometry is the only available examination.

The required input data are flow-volume measurements usually available in output reports provided by standard spirometers. (i.e. flow values, FVC). DLco% is not required for this analysis.

Recently, the performances achieved by the current real-time ESI software have been studied on a large international database of smokers, ex smokers, COPD patients and the results obtained during the experimentation are very interesting.

For info and details about validation of the ESI software for the assessment of emphysema severity in a large population of smokers, ex-smokers and subjects with COPD please read the following paper (Respiratory Research, 2020):

Validation of a method to assess emphysema severity by spirometry in the COPDGene study


Recently, the ESI emphysema severity index software was used to calculate ESI index in a wide Swedish population (4.000 subjects).  Authors found that ESI was significantly correlated to respiratory death but not non-respiratory death, while other standard variables as: high age, male sex and low FEV1 was associated with non-respiratory as well as respiratory death. Current smoking habits increased the hazard of respiratory death but did not reach significance (p 0.066). They found that  one unit increase in ESI increased hazard rate of all-cause death by 20% (p 0.0002) and hazard ratio of respiratory death by 57% (p <0.0001).

Related papers:

  • Luoto J, Pihlsgård M, Pistolesi M, Paoletti M, Occhipinti M, Wollmer P, Elmståhl Sö, Emphysema severity index (ESI) associated with respiratory death in a large Swedish general population, Respiratory Medicine (2022), doi: