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Legionella pneumonia — SCE Acute Medicine MCQ

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EasyAcute Respiratory PresentationsLegionella pneumoniaSCE Acute Medicine

A 61-year-old man is assessed on the acute medical unit. He has high fever, diarrhoea, confusion and hyponatraemia after staying in a hotel. Chest radiograph shows multilobar consolidation. Initial assessment includes relevant observations, bedside tests and urgent blood results. What is the most appropriate investigation?

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Correct answer: B — Urinary legionella antigen

Urinary legionella antigen is the best answer because the systemic features and hyponatraemia suggest Legionella, for which urinary antigen gives a rapid supportive diagnosis. Arterial blood gas with lactate is plausible, but it is less appropriate for the physiology or timing described in this stem. The other distractors either fit a neighbouring presentation, delay definitive treatment, or miss the key immediate risk. Clinical pearl: Legionella often presents with gastrointestinal and neurological features.

Reference: BTS CAP guideline