ABSTRACT
Background: After 4 months we have shown, that DLCO is lower in severe COVID-19 patients compared to nonsevere (Guler SA, et al. Eur Respir J. 2021 Apr 29;57(4):2003690). Contributing factors are unclear. Calprotectin is an inflammatory marker released by activated neutrophils and is increased in acute severe COVID-19. Aim(s): We hypothesized that circulating calprotectin correlates with persistent lung functional impairment after COVID-19. Method(s): Calprotectin serum levels were measured in 124 patients (50% male) 4 months after COVID-19 (NCT04581135). Calprotectin was correlated with clinical parameters (Spearman's correlation). Multivariate linear regression (MLR) was performed to evaluate the independent association of calprotectin in different models. Result(s): Post-ICU patients (72% male) compared to non-ICU were significantly older (age 59.4 +/- 13.6 vs 49.2 +/- 13.1 years) and more obese (BMI 28.7 +/- 4.5 vs 25.2 +/- 6.0 kg/m2) (p=0.001, each) compared to non-ICU. DLCO was lower in post-ICU patients (75.96 +/- 19.05 %-predicted) compared to non-ICU (p<0.01). Calprotectin was significantly higher in post-ICU patients (2.74 +/- 1.15 mug/ml) compared to non-ICU (1.81 +/- 0.94 mug/ml, p<0.001). In unadjusted analysis, calprotectin correlated with DLCO (r=-0.350, p<0.001) and FVC (r=-0.417, p<0.001). In MLR adjusted for age, sex and BMI, calprotectin correlates with DLCO (R2=0.276, p<0.001). Calprotectin significantly predicted DLCO (beta=-6.463, p=0.001). Conclusion(s): Serum calprotectin is higher in post-ICU patients compared with non-ICU 4 months after COVID-19. The relationship between calprotectin levels and DLCO suggests a potential role for calprotectin in persisting lung functional impairment.