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Low TLCO in emphysema — SCE Respiratory MCQ

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ModerateRespiratory physiologyLow TLCO in emphysemaSCE Respiratory

A 65-year-old smoker has dyspnoea and emphysema on CT. Spirometry shows FEV1 55% predicted and FEV1/FVC 0.58. TLCO is 32% predicted, VA is mildly reduced and KCO is 38% predicted. There is no anaemia and echocardiography is normal. What is the most likely underlying cause?

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Correct answer: D — Loss of alveolar-capillary surface area from emphysema

The best answer is “Loss of alveolar-capillary surface area from emphysema”. The clinical pattern, physiology and imaging described are most consistent with Loss of alveolar-capillary surface area from emphysema. The competing diagnoses may share individual findings, but do not account for the complete combination in the stem. The remaining choices—“Intra-alveolar haemorrhage increasing gas transfer”, “Respiratory muscle weakness with preserved membrane”, “Extrapulmonary restriction from obesity”, “Poor effort as the sole explanation”—are credible in related respiratory presentations, but each addresses a different diagnostic, staging or management decision and does not fit the decisive findings and pathway position in this stem.

Reference: NICE NG115 chronic obstructive pulmonary disease: https://www.nice.org.uk/guidance/ng115/chapter/Recommendations