The discriminative capacity of CRP concentrations regarding COVID-19 was slightly lower than that of serum free thiol concentrations (AUC = 0.66, CI 0.51–0.81, p = 0.042) or CRP and serum free thiol concentrations combined (AUC = 0.68, CI 0.53–0.83, p = 0.020). The gene discussed is CRP; the disease is COVID-19.