UTILITY OF NOVEL FLOW VOLUME LOOP INDEXES IN DIAGNOSING AIRFLOW OBSTRUCTION

Abstract

SESSION TITLE: Obstructive Lung Disease Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: Spirometry testing has a relatively low sensitivity for diagnosing airflow obstruction in asthma. Furthermore, it is known that patients with airflow obstruction tend to demonstrate coving on their flow-volume loops. Quantitative measurements of coving-related indices may perhaps improve our ability to diagnose airflow obstruction in asthma. Our study sought to compare the performance of established spirometric indices of obstruction with novel indices derived from flow volume loops using ROC analysis. To our knowledge, this is the first study to employ asthmatic patients with age and gender matched controls to compare the global performance of criteria for airflow obstruction. METHODS: This is a retrospective case-control study. Controls were obtained from another IRB-approved study (REVORE). In this study, normal subjects were selected based on responses to an in-depth questionaire asking about symptoms of asthma. Those who reported no symptoms underwent formal pulmonary function testing, including spirometry with bronchodilator challenge. For our study, we selected participants who had normal spirometry, lung volumes and diffusion capacity to act as controls. We then selected age- and gender-matched patients from an IRB-approved cohort (LUVA) of patients with asthma. As part of the LUVA study, all subjects had spirometry, lung volume and diffusion capacity measurements. Flow-volume loops were analyzed for cases and controls using a free online graphing software package (GeoGebra). Several measurements of each flow-volume loops were taken, includingthe distance from the point of peak expiratory flow to the point along the expiratory curve at which coving was most pronounced (point of maximal deflection, or PMD). ROC and AUC analyses were performed in SPSS version 25 to compare (1) PMD in cases versus controls, (2) magnitude of deflection at PMD in cases versus controls (MOD), and (3) FEV1/FVC ratio in cases versus controls. The ROC and AUC of the new indices were compared to those of FEV1/FVC ratio. RESULTS: 13 controls were matched to 20 cases. The male to female ratio was 7:6. Mean age, height and weight were similar between groups. The AUC for PMD was 0.876 (95%CI 0.740-1.011). At a cutoff of 0.715, the sensitivity and specificity were 76.9% and 92.3%, respectively. The AUC for MOD was 0.858 (95%CI 0.682-0.984). At a cutoff of 2.735, the sensitivity and specificity were 84.6% and 76.9%, respectively. AUC for FEV1/FVC ratio was 0.870 (95%CI 0.711-1.029). At a cutoff of 0.738, the sensitivity and specificity were 76.9 and 100%, respectively. CONCLUSIONS: PMD was the best overall criteria for diagnosing obstruction in asthma. These findings need confirmation in a larger cohort of asthmatics matched for gender and age. CLINICAL IMPLICATIONS: These indices may have the potential to improve our ability to identify patients who may benefit from asthma therapies. DISCLOSURES: No relevant relationships by Eric Day, source=Web Response No relevant relationships by Evanpaul Gill, source=Web Response no disclosure on file for Sneha Gullapalli; No relevant relationships by Viraj Jain, source=Web Response No relevant relationships by Kara Schmidt, source=Web Response no disclosure submitted for Jose Vempilly