MX1 and bacterial infectious disease: At a cutoff value of 4.7, the MxA/CRP ratio achieved a Se, Sp and a LR- of 84.6% [95% CI 66.5–93.9%], 100% [95% CI 87.1–100%] and 0.15% [95% CI 0.1–0.4] (Fig. 3d) for differentiating viral and bacterial infections.