By América Torres
Emphysema detected by CT scan has a new marker of severity. It is the ESI index (Emphysema Severity Index) a novel marker (based on spirometry) that still has no clear clinical validity. Despite this, it provides information that has made it possible to establish a relationship between this index and death from respiratory causes.
Johannes Luoto et al. conducted the study "Emphysema severity index (ESI) associated with respiratory death in a large Swedish general population" to try to obtain more information about ESI. Here's what they found.
Advantages of ESI in the treatment of emphysema
Advantages of ESI in the treatment of emphysema
The theory that the presence of emphysema altered the Maximal Expiratory flow/volume curve (MEFV) is not new, it was first put forward in 1976. It was suggested that the loss of elastic recoil, a positive pleural pressure, structural weakness in the walls of the major airways and high bronchiolar resistance caused a loop in the downward zone of the MEFV curve.
The authors of the study took up this theory to try to make the ESI serve to quantify the change of this loop and have a system for measuring the level of emphysema in a range of 0 to 10. The idea was to propose ESI index as a useful marker of the presence and severity of emphysema. To obtain this, they used data taken from spirometry and correlated the marker with the estimated level of emphysema shown by a CT scan.
Their goal was to find out whether elevated ESI could be a cause of mortality and whether such elevation could increase the risk of death at 10 years from respiratory causes.
It should be noted that studies on the clinical impact of ESI have not yet been published. Therefore, spirometry values, such as FEV1, FEV1 and FVC, remain the main measures to establish the severity of airway obstruction.
In addition, the authors consider that to achieve the ESI it is necessary to perform a spirometry. This means that this new index could be easily implemented and could be used together with the already known values of spirometry test.
Methodology
Methodology
This clinical trial, called "Study on Aging and Care (SNAC)", was conducted in the province of Skåne, Sweden. A total of 4,453 subjects belonging to the rural and urban population randomly selected participated. Only 3,974 people were included in the final analysis.
- Three groups were selected. Cohort I with individuals aged 60-95 years at baseline, who had undergone baseline tests in 2001. Cohort II, individuals aged 60-81 years with baseline tests in 2006. Cohort III, individuals 60-81 with baseline tests in 2012.
- The overall response rate was 71%.
- The inclusion criterion was, at least, one acceptable spirometry according to the criteria of the American Thoracic Society.
- Participants were re-examined every 3-6 years, depending on their age. This study is still ongoing, so the most recent exams were conducted in 2017.
- Mortality data were obtained from the Swedish Cause of Death Register. Only the primary cause of death was considered for this clinical trial.
- Researchers used Cox Regression Analysis to assess the impact of the ESI index on mortality risk, both respiratory and non-respiratory, 10 years after the baseline test. In addition to the ESI, the analysis was adjusted for age, smoking, sex and FEV1/FVC and FEV1..
Results
- The researchers classified the risk factors into 3:1 Factors that increased the risk of respiratory death. 2 Factors that increased the risk of non-respiratory death. 3 Factors that rose the risk of both, respiratory and non-respiratory, death.
- The ESI index correlated significantly to respiratory death but had nothing to do with non-respiratory deaths.
- Being male and a low FEV1 were associated with both, respiratory and non-respiratory death.
- Smoking increased the hazard of respiratory death, but not significantly (p 0.066).
- An increase of one unit of ESI rose the risk of death from all causes by 20% and the risk of respiratory death by 57%.
- FEV1/FVC was not associated with all-cause mortality nor respiratory death.
Relationship between ESI index and emphysema
Relationship between ESI index and emphysema
According to the authors of this work, the study "Spirometric assessment of emphysema presence and severity as measured by quantitative CT and CT-based radiomics in COPD" showed that the ESI index correlates with the severity of emphysema measured by CT.
Likewise, they affirm that the ESI methodology has also been validated in smokers of diverse ethnic origins (who participated in the COPDgene study). And they consider that these clinical outcomes are a step toward demonstrating the usefulness of ESI.
Spirometry is underrated
Spirometry is underrated
This study, which proposes a new marker of quantification of pulmonary emphysema, demonstrates the multiple possibilities of spirometry.
At SCHILLER we have developed the SpiroScout to make spirometry a safe, reliable, simple, affordable, and comfortable test to take care of lung health of patients. Unfortunately, primary care physicians do not perform it as often as they should, which could be useful to detect various respiratory conditions in time.
Spirometry should be routinary in primary care contacts.
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