Procalcitonin Antibiotic Consensus Trial (ProACT)

A procalcitonin (PCT) will be drawn level within one hour after randomization in the ED, and if hospitalized, 6-24 hours after the initial ED blood draw, and on Days 3, 5, and 7. Days 3, 5, and 7 blood draws for procalcitonin will only occur in hospitalized patients on antibiotics and/or at the treating physician's discretion.

In the ED, we will quickly (\<1 hour goal) provide clinicians the procalcitonin result.

"Procalcitonin antibiotic guideline --~Procalcitonin level (ug/L) -- Bacterial etiology -- Recommendation~\< 0.1 -- Very unlikely -- Antibiotics strongly discouraged(1)~0.1 - 0.25 -- Unlikely -- Antibiotics discouraged(1)~\> 0.25 - 0.5 -- Likely -- Antibiotics recommended(2)~\> 0.5 -- Very likely -- Antibiotics strongly recommended(2)~1. Initial antibiotics can be considered for critical illness, Legionella pneumophilia. Procalcitonin should be evaluated in context with all findings and the total clinical status; clinical judgment always necessary.~2. For outpatients, antibiotic duration based on level (\> 0.25-0.5 ug/L:3 days; \> 0.5-1.0 ug/L:5 days; \>1.0 ug/L:7 days). Physician follow-up is recommended."

We will collect the number of antibiotic days during telephone visits occurring on or around Day 15 and Day 30