uk-fficm MCQ (SBA): Procalcitonin in Sepsis

A 62-year-old man on ICU develops a new fever on day 14 with rising procalcitonin (PCT from 0.3 to 8.5 µg/L). CRP rises from 45 to 220. He has a central line, urinary catheter, and chest drain. Blood cultures, urine, and drain fluid cultures are all taken. In the context of ICU-acquired infection, what does a procalcitonin >2 µg/L most reliably suggest?