Not Every Rise in Procalcitonin is Infection

Introduction: Procalcitonin (PCT) is produced by thyroid and neuro-endocrine cells of the lung and the intestine. Measurement of PCT can be used as a marker of severe sepsis caused by bacteria and generally grades well with the degree of sepsis. PCT is used increasingly as a marker of bacterial infection, with PCT >2 ng/mL advocated as an indicator to initiate antibiotics in patients with presumed infection. However, not every elevated PCT is an infection. Case: 49 year-old women presented in July with fever, nausea, vomiting, confusion, headache, light-headedness, neck stiffness and abdominal pain for one day. Her past medical, family and social history were non-contributory. Examination revealed fever (99.5 °F), tachycardia (pulse 115/min) and dry oral mucosa. Labs showed high white blood cell (WBC) count-18,000/mm3, PCT-145.88 ng/mL, Aspartate transaminases (AST) -560 units/L, Alanine transaminases (ALT)-213 units/L and Alkaline phosphatase (ALP)–201 units/L. She was hydrated and antibiotics started after drawing blood cultures and lumbar puncture. Urinalysis, Computed Tomography (CT) scan of head, lumbar puncture, chest X-ray and CT scan of abdomen and pelvis were non-contributory. Blood cultures and viral meningitis panel was negative. Next day, she became afebrile, WBC dropped to 11,300/mm3, PCT- 92.3 ng/mL, AST-57 units/L, ALT-86 units/L and ALP-111 units/L. She reported being in the sun, the entire preceding day, while moving to new apartment in 95 ºF heat and not drinking any fluids. She was diagnosed with heat stroke, hydrated and antibiotics stopped. She responded well and was discharged next day. Discussion: She had highly elevated PCT without any infectious etiology. Her PCT trended downwards the next day, thus correlating with PCT's half-life of 25-30 hours. Heatstroke usually presents clinically with systemic inflammatory response syndrome and can have elevated PCT and transaminases. Thus, in patients with high PCT, clinicians should be equally vigilant for non-infectious inflammatory etiologies.