Validation of the RIM Score-COVID in the Spanish SEMI-COVID-19 Registry

Abstract

The significant impact of COVID-19 worldwide has made it necessary to develop tools to identify patients at high risk of severe disease and death. This work aims to validate the RIM Score-COVID in the SEMI-COVID-19 Registry. The RIM Score-COVID is a simple nomogram with high predictive capacity for in-hospital death due to COVID-19 designed using clinical and analytical parameters of patients diagnosed in the first wave of the pandemic. The nomogram uses five variables measured on arrival to the emergency department (ED): age, sex, oxygen saturation, C-reactive protein level, and neutrophil-to-platelet ratio. Validation was performed in the Spanish SEMI-COVID-19 Registry, which included consecutive patients hospitalized with confirmed COVID-19 in Spain. The cohort was divided into three time periods: T1 from February 1 to June 10, 2020 (first wave), T2 from June 11 to December 31, 2020 (second wave, pre-vaccination period), and T3 from January 1 to December 5, 2021 (vaccination period). The model's accuracy in predicting in-hospital COVID-19 mortality was assessed using the area under the receiver operating characteristics curve (AUROC). Clinical and laboratory data from 22,566 patients were analyzed: 15,976 (70.7%) from T1, 4,233 (18.7%) from T2, and 2,357 from T3 (10.4%). AUROC of the RIM Score-COVID in the entire SEMI-COVID-19 Registry was 0.823 (95%CI 0.819-0.827) and was 0.834 (95%CI 0.830-0.839) in T1, 0.792 (95%CI 0.781-0.803) in T2, and 0.799 (95%CI 0.785-0.813) in T3. The RIM Score-COVID is a simple, easy-to-use method for predicting in-hospital COVID-19 mortality that uses parameters measured in most EDs. This tool showed good predictive ability in successive disease waves.

Keywords: COVID-19; Hemogram-derived ratios; Mortality; Neutrophil-to-platelet ratio; Risk factors; Score; Spain.

Fig. 1

Nomograms of the NPR model. SpO2 (%): oxygen saturation; NPR (high: > 3.0) neutrophil-to-platelet ratio; CRP (high: > 112 mg/L): C-reactive protein

Fig. 2

Patient inclusion flowchart. CRP C-reactive protein; SpO₂ oxygen saturation

Fig. 3

AUC charts of the NPR RIM Score-COVID in the Spanish SEMI-COVID-19 Registry calculated for the total number of patients included (A) and for each time period (B, C, D). T1 first time period from February 1 to June 10, 2020 (B), T2 second time period from June 11 to 31 December 31, 2020 (C) T3 third time period from January 1 to December 5, 2021 (D); NPR, neutrophil-to-platelet ratio