Timing of Tocilizumab Use and COVID-19

Dear Editor,

We would like to share ideas on “Impact of Timing of Tocilizumab Use in Hospitalized Patients With SARS-CoV-2 Infection.”¹ Singh et al concluded that early use of anti-interleukin 6 therapy may be associated with improved hospital mortality and reduction in progression to more severe COVID-19. Tocilizumab is a possible useful drug for management of COVID-19. Since this was a retrospective study, it is difficult to control for confounding factors. Matching for groups might be useful. However, some parameters might also be confounded. For example, in some areas of the world, ferritin levels might be confounded by thalassemia or parasitic infestation.^2-3 Nevertheless, those 2 disorders are not common in areas such as New York City. In the United States, metabolic syndrome might be a more important source of confusion with ferritin levels.⁴

Also, various alternative therapies given to patients might affect outcome in the present study. Combining tocilizumab with systemic steroid therapy may produce more favorable outcomes. Different types of respiratory support also affect these rates.⁵ Different respiratory support also affects outcome of therapy.⁶ Moreover, in the present report, Singh et al¹ mentioned only that there was no improvement in clinical outcome if the drug was given at the time the subject required respiratory support. According to a recent report, reductions in mortality risk vary depending on the level of support at tocilizumab start, including stratifications for conventional oxygen therapy, noninvasive ventilation, invasive ventilation, and no support.⁶ In a recent report, it was found that the maximal dose limit was sufficient in the management of obese subjects.⁷ Finally, the present report cannot reflect actual time that the drug was given. The illness period of subject, including prehospitalization, might be variable and it cannot decide whether drug was given early or not.

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