Which is the best test to detect pulmonary embolism

CTPA is the first-line diagnostic test. It has the advantage of visualising the distribution and extent of the emboli or highlighting an alternative diagnosis, such as consolidation, pneumothorax or aoic dissection. The sensitivity of CT scanning may be increased by simultaneous visualisation of the femoraland popliteal veins, although this is not widely practised. As the contrast media may be nephrotoxic, care should be taken in patients with renal impairment, and CTPA avoided in those with a history of allergy to iodinated contrast media. In these cases, either V/Q scanning or ventilation/perfusion single photon emission computed tomography (V/Q SPECT) may be considered Ref Davidson edition23rd pg 620