Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1161 page)

   Differential diagnosis of community-acquired bacterial versus viral pneumonia

   Monitoring of therapeutic response to antibacterial therapy

   Interpretation

   Procalcitonin levels above 2.00 ng/mL on the first day of ICU admission represent a high risk for progression to severe sepsis and/or septic shock.

   PCT for initiation of antimicrobial therapy

   PCT result <0.50 μg/L—initiation of antimicrobial therapy may not be indicated. Consider a noninfectious cause of the clinical syndrome. If antibiotics are withheld, may want to repeat PCT level in 6 hours to rule out an increase that would suggest antibiotic therapy is warranted

   PCT result 0.50–1 μg/L—initiation of antimicrobial therapy encouraged

   PCT result >1 μg/L—initiation of antimicrobial therapy strongly encouraged

   Limitations

   Procalcitonin levels in the serum are elevated in a variety of inflammatory conditions, including bacterial infection, malaria, burns, pancreatitis, and traumatic injury.

   Levels rise within 2–4 hours, peak generally in the 2nd day, and fall rapidly during recovery.

   Procalcitonin levels are generally not as high in fungal or viral infection.

PROGESTERONE

   Definition