PCT levels peaked on day 1, returned to normal values on day 3, and were higher in infected versus non-infected patients.PCT levels correlated to SAPS II score. PCT in patients with septic shock was always greater than 10 ng/ml.CRP levels were high in all patients and did not correlate to PCT.PCT levels were similar in Gram-positive versus Gram-negative infection.PCT levels were higher in septic versus cardiogenic shock.PCT: cut-off 1 ng/ml, sensitivity 85%, specificity 95% in predicting infection.CRP: cut-off 150 mg/l, sensitivity 64%, specificity 84% in predicting infection. This evidence concerns the gene CALCA and infection.