D-Dimer in pulmonary embolus diagnosis

I recently saw a case of a young lady for shortness of breath. No other medical issues, only medication was oral contraceptives. No family history of blood clots. Chest X-ray clear, no desaturations on room air. My pre-test probability for pulmonary embolus was quite low, however she was concerned and asked to be “checked for a blood clot”. With such a low index of suspicion, I did not think it warranted a CT-PA or a V/Q scan (which would have required an ER visit since it was after-hours), and was wondering what the current data was on the efficacy of a simple D-Dimer test.

Conveniently, a recent Annals of Interal Medicine article did a systematic review on this, suggesting that: “For excluding PE or DVT, a negative result on quantitative rapid [D-dimer] ELISA is as diagnostically useful as a normal lung scan or negative duplex ultrasonography finding.”

So, she was sent to our local hospital, received a negative D-Dimer test in 15 minutes, with both of us being reassured of a very low likelihood of a clot.

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