Nonspesific bronchial hyperresponsiveness and eosinophilic airway inflammation predict occupational asthma to HMW agents but not to LMW agents

<bold>Background:</bold> Specific inhalation challenge (SIC) is used to differentiate occupational asthma (OA) from work-exacerbated asthma (WEA). Clinical differences between these two conditions are not fully recognized. <bold>Methods:</bold> We reviewed medical records of 616 asthma patients who were examined with SIC test in 2010-2020 because of OA suspicion. We compared clinical baseline characteristics between OA and WEA patients and identified predictive markers for OA. <bold>Results:</bold> Altogether 264 patients had positive SIC (OA) and 352 patients had negative SIC (WEA) (Table). Nonspecific bronchial hyperresponsiveness (NSBHR) (OR 3.22 (CI 1.59-6.52) and Fractional exhaled nitric oxide (FeNO) ≥25 (5.45 (2.25-13.24) predicted OA in patients exposed to high molecular weight (HMW) agents after adjusting for age, BMI, sex and current smoking. However, there were no difference between OA and WEA among those exposed to low molecular weight (LMW) agents: NSBHR OR 1.21 (0.74-1.99), FeNO ≥ 25 OR 0.89 (0.50-1.60). <bold>Conclusions:</bold> NSBHR and eosinophilic airway inflammation seem to increase likelihood of OA in patients exposed to HMW agents but not in patients exposed to LMW agents. <table-wrap><object-id>erj;64/suppl_68/PA3112/TB1</object-id><object-id>T1</object-id><object-id>TB1</object-id><table><colgroup><col></col><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td></td><td>All<break></break>n=616</td><td>OA<break></break>n=264</td><td>WEA<break></break>n=352</td><td>p-value</td></tr><tr><td>Age, mean (SD)</td><td>41.6(11.4)</td><td>40.7(11.4)</td><td>42.3(11.5)</td><td>0.457</td></tr><tr><td>Male (%)</td><td>306(50.5)</td><td>127(48.7)</td><td>179(51.9)</td><td>0.432</td></tr><tr><td>BMI, mean (SD)</td><td>27.54(5.35)</td><td>27.7(5.47)</td><td>27.4(5.27)</td><td>0.396</td></tr><tr><td>Current smoking (%)</td><td>134(22.2)</td><td>68(26.2)</td><td>66(19.2)</td><td>0.041</td></tr><tr><td>FEV1 % predicted, mean (SD)</td><td>87.3(11.8)</td><td>87.8(11.9)</td><td>87.0(11.8)</td><td>0.367</td></tr><tr><td>Atopy (%)</td><td>251(44.7)</td><td>128(54.0)</td><td>123(42.9)</td><td><0.001</td></tr><tr><td>Antigen type LMW (%)</td><td>380(61.9)</td><td>106(40.3)</td><td>274(78.1)</td><td><0.001</td></tr><tr><td>FeNO ≥ 25 (%)</td><td>145(26.3)</td><td>76(32.6)</td><td>69(21.7)</td><td>0.004</td></tr><tr><td>NSBHR (%)</td><td>247(40.1)</td><td>126(43.1)</td><td>121(43.1)</td><td>0.002</td></tr></tbody></table></table-wrap>