Abstract
BACKGROUND AND AIMS: Tocilizumab, an anti-inflammatory agent used in severe COVID-19 infection, is known to inhibit the Interleukin 6 receptor and reduce C-reactive protein (CRP) resulting in an increased risk of secondary infections. However, the trend of secondary infection and the relative inflammatory response after tocilizumab use has been reported variably. METHODS: In this observational cross-sectional study, the time to normalization of CRP, rate of secondary infections, significance of infection indicators (CRP and white blood cell (WBC) count) at the time of secondary infections, length of intensive care unit (ICU) stay, and survival rate were evaluated in patients with severe COVID-19 infection after tocilizumab use. RESULTS: A total of 216 patients (118 tocilizumab receivers vs. 98 nonreceivers) were included in this study. A higher rate of blood-stream infection (p 0.02), shorter ICU stay (p < 0.001) regardless of tocilizumab dose, and a slower rate of CRP normalization (p 0.009) were observed for tocilizumab receivers. The survival rate was not different between the two groups. A rise in CRP level was absent for tocilizumab receivers (p < 0.001) at the time of developing a secondary infection, while elevated WBC count was evident for both groups without any significant difference. CONCLUSION: Tocilizumab can increase the risk of secondary infections, while CRP levels may remain suppressed at the time. Therefore, CRP may not be suggested as a reliable marker of infection in tocilizumab users, although WBC count may remain a consistent value in confirming secondary infections in this population.