Type2 and non-type2 inflammatory characteristics after mild COVID-19

<italic><bold>Background:</bold></italic> The Post-COVID-Syndrome (PCS) score developed by Bahmer T et al. (eClinicalMedicine, 2022) allows severity classification of PCS patients. While low-grade systemic inflammation might play a role in PCS pathophysiology, type2 inflammatory diseases such as asthma might mimic PCS symptoms. <italic><bold>Objective:</bold></italic> We aimed to quantify type2 (FeNO; blood eosinophils) and non-type2 inflammation (CRP; neutrophil/lymphocyte ratio, NLR) in patients after mild COVID-19. <italic><bold>Methods:</bold></italic> Participants were part of the multicenter, prospective, population-based COVIDOM study. On-site visits were scheduled ≥6 months after PCR-confirmed and usually mild acute COVID-19 (hospitalization rate <10% in total). According to the PCS score, participants were grouped into none/mild (I), moderate (II) and severe PCS (III). <italic><bold>Results:</bold></italic> Of 1448 participants with complete FeNO measurements only 3.6% had ≥50ppb. Participants in PCS-III had lower FeNO values and higher CRP and NLR, while EOS were similar (table 1). All differences were within the normal range. Differences in FeNO were not explained by smoking status or steroid usage. <table-wrap><object-id>erj;64/suppl_68/PA5263/T1</object-id><object-id>T1</object-id><object-id>t1</object-id><table><colgroup><col></col><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td><italic>Table 1</italic></td><td>PCS-I</td><td>PCS-II</td><td>PCS-III</td><td>p-value</td></tr><tr><td>FeNO</td><td>21±17</td><td>19±14</td><td>17±11</td><td>0.006</td></tr><tr><td>EOS</td><td>0.16±0.19</td><td>0.16±0.14</td><td>0.16±0.19</td><td>>0.05</td></tr><tr><td>CRP</td><td>1.6±3.7</td><td>2.1±3.1</td><td>2.8±4.8</td><td><0.001</td></tr><tr><td>NLR</td><td>2.1±1.0</td><td>2.2±1.1</td><td>2.4±1.3</td><td><0.001</td></tr></tbody></table></table-wrap> <italic><bold>Conclusion:</bold></italic> While patients with mild acute COVID-19 and self-reported PCS symptoms demonstrated slightly increased systemic inflammatory markers, type2 inflammation was not elevated or – in terms of FeNO – even decreased. Therefore, measurement of CRP and differential blood count are relevant markers in PCS assessment, while FeNO measurement might only be applied in patients with known or suspected bronchial asthma.