The current study found gamma-glutamylthreonine to be a risk factor for prostate cancer,[39] a protective factor for systemic lupus erythematosus,[40] and the best categorical variable for new cases of tuberculosis.[41] Although our study implied that gamma-glutamylthreonine may not be a mediator of the causal relationship between IL-18 and COVID-19, it also suggested that gamma-glutamylthreonine may exacerbate the course of COVID-19. Here, IL18 is linked to systemic lupus erythematosus.