Investigating sepsis with biomarkers

A 65 year old man presents with lethargy, fever, and rigors. On examination his arterial blood pressure is 120/50 mm Hg, he has a mild tachycardia (105 beats/min), and he is febrile (38.7°C), with no other abnormalities. His urine is cloudy and urinary dipstick test shows the presence of leucocytes and nitrate. There is no history of recent travel, urinary symptoms, or drug allergy (including antibiotic sensitivity) and no relevant findings on systems review (such as liver or kidney disease). You promptly establish intravenous access, draw blood for laboratory tests (including blood culture), send a urine sample for microbiology, and administer the first dose of an empirical broad spectrum antibiotic.

These clinical signs and symptoms strongly suggest sepsis. However, in a third of patients with sepsis, the causative pathogen cannot be identified.1 The lack of confirmatory evidence of infection often makes the diagnosis of sepsis a challenge. This difficulty is reflected by the inclusion of the words “probable infection” in defining sepsis in the Surviving Sepsis Campaign guidelines (box 1).2