Prognostic Factors and Clinical Prediction Score for Progressive Respiratory Failure in Severe COVID-19 Pneumonia Patients Treated with Tocilizumab: A Multicenter Study

Abstract

Purpose: A proportion of COVID-19 pneumonia patients develop respiratory failure despite tocilizumab administration. This retrospective cohort study aimed to identify prognostic factors associated with progressive respiratory failure within 14 days among patients with severe COVID-19 pneumonia treated with Tocilizumab and to describe treatment outcomes. Patients and Methods: Patients with severe COVID-19 pneumonia were assessed, and their demographic, clinical, laboratory data, and prior treatment were collected on the day of tocilizumab administration. A multivariable Cox proportional hazard model was employed to identify prognostic factors. Results: Of the 109 patients, 32 (29.4%) progressed to respiratory failure. We identified the following independent prognostic factors for progressive respiratory failure: pulse oximetry saturation to fraction of inspired oxygen ratio (SpO<inf>2</inf>/FiO<inf>2</inf>) ≤ 160 (HR 2.97, 95% CI 1.41–6.23, P = 0.004), estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m² (HR 3.21, 95% CI 1.23–8.39, P = 0.017), and serum potassium ≤ 4 mmol/L (HR 2.82, 95% CI 1.38–5.80, P = 0.005). A predictive model based on these factors effectively stratified the risk of progressive respiratory failure (area under the curve = 0.72, 95% CI 0.63–0.80). Patients experiencing progressive respiratory failure had poor clinical outcomes, with a mortality rate of 62.5%, compared to 0.0% in the non-respiratory failure group (p < 0.001). Conclusion: In severe COVID-19 pneumonia patients treated with Tocilizumab, low SpO<inf>2</inf>/FiO<inf>2</inf> ratio, low eGFR, and relatively low serum potassium were independent predictors for progressive respiratory failure. This simple clinical score may help identify high-risk patients early, though external validation is required before routine implementation.