Interleukin-6-based mortality prediction model for COVID-19: validation and update in multicentre and second wave cohorts

Utrero-Rico, Alberto; Ruiz-Hornillos, Javier; González-Cuadrado, Cecilia; Rita, Claudia Geraldine; Almoguera, Berta; Minguez, Pablo; Herrero-González, Antonio; Fernández-Ruiz, Mario; Carretero, Octavio; Taracido-Fernández, Juan Carlos; López-Rodriguez, Rosario; Corton, Marta; Aguado, José María; Villar, Luisa María; Ayuso-García, Carmen; Paz-Artal, Estela; Laguna-Goya, Rocio

Background Coronavirus disease 2019 (COVID-19) is a highly variable condition. Validated tools to assist in the early detection of patients at high risk of mortality can help guide medical decisions. Objective To validate externally, as well as in patients from the second pandemic wave in Europe, our previously developed mortality prediction model for hospitalized COVID-19 patients. Methods Three validation cohorts were generated: two external with 185 and 730 patients from the first wave and one internal with 119 patients from the second wave. The probability of death was calculated for all subjects using our prediction model, which includes SpO2/FiO2 ratio, neutrophil-to-lymphocyte ratio, LDH, interleukin-6 and age. Discrimination and calibration were evaluated in the validation cohorts. The prediction model was updated by re-estimating individual risk factor effects in the overall cohort (N=1477). Results The mortality prediction model showed good performance in the external validation cohorts 1 and 2, and in the second wave validation cohort 3 (AUC 0.94, 0.86 and 0.86, respectively), with excellent calibration (calibration slope 0.86, 0.94 and 0.79; intercept 0.05, 0.03 and 0.10, respectively). The updated model accurately predicted mortality in the overall cohort (AUC 0.91), which included patients from both the first and second COVID-19 waves. The updated model was also useful to predict fatal outcome in patients without respiratory distress at the time of evaluation. Conclusions This is the first COVID-19 mortality prediction model validated in patients from the first and second pandemic waves. The COR+12 online calculator is freely available to facilitate its implementation (https://utrero-rico.shinyapps.io/COR12_Score/)