Procalcitonin: When It Helps, When It Doesn't, and When It Fools You
Procalcitonin: When It Helps, When It Doesn't, and When It Fools You The antibiotic stewardship tool that's powerful in the right context and useless in the wrong one. Procalcitonin (PCT) is a peptide precursor of calcitonin that rises specifically in response to bacterial infection and remains low in viral infections and most autoimmune flares. It's gained traction as an antibiotic stewardship tool, but it's only useful in specific clinical scenarios—and ordering it indiscriminately creates more confusion than clarity. How It Works In health, PCT is produced only by thyroid C cells and is undetectable (<0.05 ng/mL). During bacterial infection, virtually every tissue in the body begins producing PCT in response to bacterial endotoxins and pro-inflammatory cytokines. Viral infections do NOT trigger this response (interferon-gamma actually suppresses PCT production), creating the bacterial-vs-viral distinction that makes PCT clinically useful. Where PCT Changes Manag...