Phenotypic differences between Asthmatics with and without Small Airways Dysfunction (SAD) as defined by lung oscillometry and spirometry

<bold>Background:</bold> Small Airways Dysfunction (SAD) is an emerging phenotype which is reported in over 50% of asthmatics. We aimed to compare the demographic and clinical differences between SAD and non-SAD Asthma across multiple centers in India. <bold>Methods:</bold> Pulmonologists from 5 centres across India, who were members of the International Network for Lung Oscillometry Research (ARISE) took part in the study. Oscillometry was performed using the Antlia FOT (iCALTECH, Bangalore. India) and spirometry was performed using devices meeting ATS/ERS standards, among asthmatic patients visiting their clinics. SAD was defined using cut-off of ≥1 for R5-R20 or >65% for FEF25%-75%. <bold>Results:</bold> Out of data obtained from 1969 asthmatic patients, 1334 were eligible for the final analysis, of which 1069 (80.1%) had SAD. Phenotypic differences between SAD and non-SAD are shown in Table 1. <bold>Conclusion:</bold> SAD asthma presents with more breathlessness, wheeze, and chest tightness than non-SAD asthma. Mild SAD is better detected on Oscillometry, while spirometry is more sensitive to diagnose moderate-severe SAD. <table-wrap><object-id>erj;64/suppl_68/PA3960/T1</object-id><object-id>T1</object-id><object-id>t1</object-id><table><colgroup><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td>Table 1: Phenotypic differences between SAD and non-SAD</td><td> <bold>SAD Asthma</bold> <bold>(n=1069)</bold> </td><td> <bold>Non-SAD Asthma</bold> <bold>(n=265)</bold> </td><td><bold>p - Value</bold></td></tr><tr><td><bold>Age (years ± SD)</bold></td><td>46.0 ± 15.5</td><td>39.6 ± 16.1</td><td>< 0.01</td></tr><tr><td><bold>Gender (F:M)</bold></td><td>53% : 47%</td><td>46% : 54%</td><td>0.029</td></tr><tr><td><bold>BMI (Kg/m2)</bold></td><td>25.4 ± 4.6</td><td>24.4 ± 4.8</td><td>0.002</td></tr><tr><td><bold>Symptoms</bold></td><td></td><td></td><td></td></tr><tr><td>Cough</td><td>67.0%</td><td>73.4%</td><td>0.046</td></tr><tr><td>Shortness of breath</td><td>69.8%</td><td>53.9%</td><td><0.01</td></tr><tr><td>Wheeze</td><td>55.7%</td><td>41.8%</td><td><0.001</td></tr><tr><td>Chest Tightness</td><td>35.8%</td><td>27.3%</td><td>0.010</td></tr><tr><td><bold>Severity (FEV1) % pred</bold></td><td></td><td></td><td></td></tr><tr><td>Mild</td><td>37.2%</td><td>88.6%</td><td><0.001</td></tr><tr><td>Moderate + Severe</td><td>62.8%</td><td>11.4%</td><td></td></tr><tr><td><bold>Oscillo “+ve” and Spiro “-ve”</bold></td><td> <bold>Mild:</bold> 78.8% <bold>Mod-Severe:</bold> 21.2% </td><td>−</td><td></td></tr><tr><td><bold>Oscillo “-ve” and Spiro “+ve”</bold></td><td> <bold>Mild:</bold> 34.6% <bold>Mod-Severe:</bold> 65.4% </td><td>−</td><td></td></tr></tbody></table></table-wrap>