The informative value of CD3+CD4+ and CD3+CD8+ T-cell count and cHIS scale as predictors of severe COVID-19 when using interleukin-6 receptor blockers in the in-hospital setting

Background. Clinical and laboratory signs of hyperinflammatory response in COVID-19 may serve as prognostic markers of the disease scenario. In real-world practice, there is an unmet need to determine the optimal timing of identifying predictors of SARS-CoV-2 adverse outcomes in the context of patient stratification to improve the effectiveness of anti-IL-6R therapy. Lymphopenia has a high informative value for the adverse prognosis of the COVID-19 course; however, the informative value of CD3+CD4+, CD3+CD8+ T-cell count remains questionable. In addition to lymphocyte phenotyping, a six-criterion additive scale (cHIS) was used in the study. 
Aim. To study the informative value of CD3+CD4+, CD3+CD8+ T-cell phenotyping and cHIS scale as predictors of severe COVID-19 when using IL-6R blockers. 
Materials and methods. A single-center, bi-directional study included 179 patients with SARS-CoV-2-induced community-acquired pneumonia with severe acute inflammation and progressing respiratory failure. Data were obtained from electronic patient records. Anti-IL-6R was administered in addition to standard therapy in the cohorts. The following disease outcomes were used to determine the informative value of the studied parameters: mortality and hospital discharge. Inflammatory markers were measured before and after administering anti-IL-6R, followed by monitoring. Statistical analysis was performed using SPSS (version 25.0). The quantitative indices were described using the median and interquartile range. Quantitative indices were compared using nonparametric methods: MannWhitney U-test, KruskalWallis test. The groups were compared by qualitative characteristics using Pearson's chi-square test. Correlation analysis of quantitative indicators was performed using Spearman rank correlation. For additional analysis of the cHIS scale, odds ratio and decision tree methods were used. Differences were considered statistically significant at р0,05. 
Results. Immunophenotyping of lymphocytes as a predictor of the severe SARS-CoV-2 requires further research. The cHIS scale may be implemented in routine clinical practice due to its high predictive value. A cHIS score of 2 on the first day of admission is a critical threshold for intensification and revision of therapy. The prognosis with cHIS is logically relevant in the first three days of hospitalization. 
Conclusion. The main result of the study is the definition of target groups of patients with community-acquired SARS-CoV-2 pneumonia for the IL-6R-blockers, considering the timing of their effective use in real clinical practice.