Interpretation of PCT level:
Up to 0.5: Systemic infection not likely.
0.5 - 2.0: Significant, but moderate systemic inflammatory response, sepsis likely.
2.0 - 10.0: Sever sepsis, sever systemic inflammatory response (SIRS), most likely due to infection, high risk of developing organ dysfunction. 
More than 10.0: important systemic inflammatory response almost exclusively due to sever bacterial sepsis or septic shock.