Study on the predictive value of laboratory inflammatory markers and blood count-derived inflammatory markers for disease severity and prognosis in COVID-19 patients: a study conducted at a university-affiliated infectious disease hospital

BACKGROUND: Since the outbreak of coronavirus disease 2019 (COVID-19), studies have found correlations between blood cell count-derived inflammatory markers (BCDIMs) and disease severity and prognosis in COVID-19 patients. However, there is currently a lack of systematic comparisons between procalcitonin (PCT), C-reactive protein (CRP), C-reactive protein-to-albumin ratio (CAR) and BCDIMs for assessing the severity and prognosis of COVID-19 patients. METHODS: A total of 1040 COVID-19 patients were included in the study. Demographics, comorbidities and laboratory results were analysed. BCDIMs refer to the following ratios: neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-C-reactive protein ratio (LCR), systemic inflammation response index (SIRI) and systemic inflammation index (SII). Disease severity and 28-day mortality are clinical outcomes of this study. Area under the curve (AUC) of receiver operating characteristic (ROC) curve was calculated for these markers, and DeLong's test compared their statistical differences. Cox regression analysis assessed their predictive value for the 28-day mortality rate. RESULTS: Among the 1040 patients, 35.3% were severe/critical, 49.6% were moderate and 15.1% were mild cases. Within 28 days, 15.1% died. The NLR had the highest predictive value for disease severity (AUC: 0.790, 95% CI: 0.762-0.818). NLR differed significantly from other markers, except LCR. LCR best predicted 28-day mortality (AUC: 0.798, 95% CI: 0.766-0.829). Some markers showed significant differences in AUC with LCR. Multivariable Cox regression identified BCDIMs, PCT, CRP and CAR as significant risk factors for 28-day mortality. CONCLUSIONS: PCT, CRP, CAR and BCDIMs, easily obtained in clinical settings, are valuable predictors of disease severity and the 28-day mortality in COVID-19 patients. The NLR is particularly effective for disease severity, while the LCR is highly predictive of 28-day mortality. These markers provide guidance for stratified management of COVID-19 patients.