CALCA and bacterial pneumonia: Cuquemelle et al. [56], in a multicenter retrospective observational study conducted in 23 French ICUs involving 103 patients with confirmed Influenza A(H1N1) pneumonia, showed that a cutoff of PCT on admission of >0.8 ng/mL, the sensitivity and specificity for distinguishing mixed viral and bacterial pneumonia were 91 and 68%, respectively.