MRCP Part 1 Investigation Decisions Lab

Case 1 · Respiratory medicine · suspected PE

INV-01

A 72-year-old woman presents with pleuritic chest pain. She is haemodynamically stable, chest radiograph shows no alternative diagnosis and the 2-level PE Wells score is 3.0. A fully quantitative D-dimer is 680 micrograms/L FEU. The local validated age-adjusted threshold is age × 10 micrograms/L FEU for patients over 50. She has no contrast allergy and renal function is normal.

Fictional results · reference intervals are supplied for this case
Investigation	Result	Reference / context
PE Wells score	3.0	PE unlikely (≤4)
D-dimer	680 micrograms/L FEU	Age-adjusted threshold 720
Observations	Stable	No shock or hypoxaemia
Chest radiograph	No alternative cause	Reviewed

What is the best next investigation strategy?A. Arrange immediate CTPA because any D-dimer above 500 is positiveB. Exclude PE using the validated age-adjusted pathway and pursue alternative diagnosesC. Repeat D-dimer every six hours until it falls below 500D. Perform invasive pulmonary angiographyE. Request leg ultrasound as a mandatory substitute for chest imaging