Objectives: One of the major challenges in treating patients with coronavirus disease 2019 (COVID-19) is predicting the severity of disease. Natural killer (NK) cells are innate lymphocytes that respond to viral infection and might relate to COVID-19 disease severity. Therefore, we aimed to develop a new predictive score for progression from mild/moderate to severe COVID-19 based on NK cells information.
Method: In total, 239 hospitalized patients with COVID-19 from two medical center in China were retrospectively included. The prognostic effects of variables, including clinical data and laboratory findings from the electronic medical records of each hospital, were analyzed using Cox proportional hazards model and Kaplan-Meier methods. A prognostic score was developed to predict progression from mild/moderate to severe COVID-19.
Results: Among the 239 patients, 216 (90.38%) patients had mild/moderate disease and 23 (9.62%) progressed to severe disease. After adjusting multiple confounding factors, pulmonary disease, age >75, IgM, CD16+/CD56+ NK cells and aspartate aminotransferase were independently predictors of progression to severe COVID-19. Based on these five factors, a new predictive score (the ‘PAINT score’) was established and showed a high predictive value (C-index = 0.91, 0.902 ± 0.021, p<0.001). The PAINT score was validated using nomogram, bootstrap internal validations, calibration curves, decision curves and clinical impact curve, all of which confirmed its high predictive value.
Conclusions: The PAINT score for progression from mild/moderate to severe COVID-19 based on NK cell information may be helpful to identify patients at high risk of progression.