Prognostic Value of Cystatin C as a Predictor of Adverse Outcome in Severe Pneumonia Associated with COVID-19

Objective. To assess the cystatin C (CysC) prognostic value for probability of death in patients with severe and extremely severe pneumonia associated with COVID-19. Material and methods. A single-center prospective study included 72 patients with severe and extremely severe pneumonia associated with COVID-19 undergoing treatment in the ICU of multifunctional medical center from September 2020 to October 2021. Recovered survivors ( N =55) were analyzed as a Group 1, nonsurvivors ( N =17) were considered as a Group 2. Results. The serum (s-CysC) and urine (u-CysC) CysC concentrations were significantly lower in Group 1 patients vs Group 2, averaging 1.31 mg/l vs 1.695 mg/l ( P =0.013550), and 0.25 mg/l vs 0.94 mg/l ( P =0.026308), respectively. Significant differences were also revealed in the subgroups differed by age ( P =0.0094), platelet count ( P =0.001), serum fibrinogen concentration ( P =0.016), as well as CURB ( P =0.02334), CRB-65 ( P =0.032564), and SOFA ( P =0.042042) scores. Therefore, s-CysC and u-CysC were statistically significant predictors of death in patients with pneumonia associated with severe and extremely severe COVID-19: 16.273 (95% CI: 2.503–105,814), P =0.003 and 1.281 (95% CI: 1.011–1.622), P =0.040, respectively. Urine and serum CysC were established as predictors of death in pneumonia associated with severe and extremely severe COVID-19, where u-CysC was defined as highly informative (ROC AUC 0.938 (95% CI: 0.867–1.000; P =0.000), with 90% sensitivity and specificity), and s-CysC — as informative (ROC AUC 0.863 (95%CI: 0.738–0.988; P =0.000) with 80% sensitivity and 72% specificity) predictive markers. Conclusion. Levels of S-CysC and u-CysC are of high prognostic significance and may contribute to identifying patients at a high risk of unfavorable outcome (death) due to pneumonia associated with severe and extremely severe COVID-19. Both S-CysC and u-CysC concentrations increasing up to 1.44 mg/l and 0.86 mg/l, respectively, were associated with high probability of death.