Clinical Predictors of Response to Tocilizumab: A Retrospective Multicenter Study

A substantial number of patients with coronavirus disease-2019 (COVID-19) demonstrate severe infection. Cytokine storm is an underlying condition that worsens clinical outcomes. As an interleukin-6 receptor antagonist, tocilizumab is a promising treatment option for COVID-19. This study aimed to evaluate the clinical predictors of mortality for critically ill COVID-19 patients receiving tocilizumab therapy.

The retrospective cohort study was conducted in 4 centers' both wards and intensive care units between March 20 and May 20, 2020. Demographic, clinical, and laboratory data were consecutively drawn from medical records. The primary endpoint was in-hospital mortality.

In this study, 39 patients (28.2% female) were included, and the mortality rate was 25.6% (n = 10). There was statistically significant difference between survivor and non-survivor groups regarding age (53.0 (46.5-65.0) vs. 75.0 (68.25-81.25), respectively,P = .001), CALL score (8.0 (7.0-10.0) vs. 12.0 (9.75-13.0), P = .001), GRAM score (119.5 (99.5-142.0) vs. 155.0 (129.8-226.0), P = .004), and white blood cell count (k/mL) (5.6 (3.8-8.6) vs. 8.0 (7.6-9.3), P = .003). The patients who were on invasive mechanical ventilation at the time of tocilizumab administration had a higher mortality rate (100% vs. 25.9%, P < .001). Besides, arterial partial pressure of oxygen/ fraction of inspiratory oxygen (PaO2/FiO2) ratio on day 7, but not on days 0, 1, and 3 of tocilizumab therapy, was associated with mortal- ity. C-reactive protein (mg/dL) tended to be lower in the survivor group; however, it was not statistically significant (68.4 (32.7-157.5) vs. 113.5 (77.7-219.0), P = .058).

This study demonstrated that advanced age, increased leukocyte count, higher CALL and GRAM scores, and the need for invasive mechanical ventilation revealed a worse prognosis after tocilizumab treatment.