ICU · diagnostics

ICU Biomarkers — Comprehensive (Procalcitonin, Lactate, Troponin, BNP/NT-proBNP)

ICU biomarkers — laboratory tests that guide diagnosis, prognosis, and treatment decisions in critically ill patients. Five key biomarkers: (1) PROCALCITONIN (PCT) — prohormone of calcitonin — rises in BACTERIAL infection (not viral/fungal/non-infectious inflammation) — used to guide antibiotic STARTING and STOPPING (PRORATA trial: PCT-guided algorithm reduced antibiotic duration by 2.7 days without adverse outcomes; threshold: 0.5 = start antibiotics, <0.5 OR fall 80% from peak = stop). (2) LACTATE — marker of tissue hypoperfusion/anaerobic metabolism — normal <2 mmol/L, elevated 2 = tissue hypoxia/shock, severe 4 = severe shock — lactate CLEARANCE (≥10% per hour) is the target (Jansen LACTATE trial). (3) TROPONIN — marker of myocyte injury — rises in MI but also in sepsis, PE, renal failure, stroke, CPR — universal in ICU patients — high-sensitivity troponin detects minor injury. (4) BNP / NT-proBNP — marker of ventricular wall stress — rises in heart failure, but also in sepsis, PE, ARDS, renal failure — diagnose HF in dyspnoea. (5) OTHER: D-dimer (PE, DIC, sepsis), CRP (inflammation), procalcitonin variants, presepsin, suPAR, mid-regional pro-adrenomedullin, lactate clearance vs central venous oxygen saturation as resuscitation target.