Several favorable randomized trials and a meta-analysis have suggested procalcitonin is a reliable and useful biomarker of infection, including in the ICU. In contrast, Jensen et al report use of a procalcitonin-driven algorithm to guide antimicrobial therapy in 9 ICUs in Denmark seemed to cause a bit of harm.
They randomized 1,200 patients to either standard care or a procalcitonin-driven strategy that used 1.0 ng/mL as an "alert" to escalate diagnostics and antibiotics. There was no difference in 28-day mortality (32%), but the procalcitonin patients spent one day longer in the ICU. Among those in the ICU, there was a 5% increase in need for mechanical ventilation, or a number needed to harm of 20 to create the need for an additional day on the vent. There was a significant but small tendency toward renal failure (relative risk 1.2 for days with GFR<60 mL/min).
Those in the procalcitonin arm received more broad spectrum antibiotics overall, but did not receive early appropriate antibiotics more often. There were no excess resistant organisms or adverse drug effects noted, and the exact mechanism of harm is unexplained.
These authors used 1.0 ng/mL as their cutoff -- but those in the above meta-analysis (which found procalcitonin helpful) used a more conservative 0.5 ng/mL as the threshold to advise augmentation of therapy.
The authors also note a 2010 randomized trial (PRORATA in Lancet) that overall showed noninferiority of procalcitonin, but which also noted an increase in organ failure and a trend toward higher mortality in the procalcitonin group in the late stage of the trial.
Jensen JU et al. Procalcitonin-guided interventions against infections to increase early appropriate antibiotics and improve survival in the intensive care unit: A randomized trial. Crit Care Med 2011;39:2048-2058.