In a patient with high clinical suspicion of pulmonary thromboembolism, the best investigation would be?

This question is a tricky one. The best method does not mean the most accurate method. Best diagnostic test means the test which has high accuracy and less disadvantages. Though invasive pulmonary angiography is the most accurate method for diagnosis of PE, it is an invasive procedure. On the other hand, CT chest with contrast is almost as accurate as invasive pulmonary angiography, for the diagnosis of PE; and it is non-invasive. Investigation of choice for PE         →  Chest CT with contrast (especially MDCTA) Investigation of 2nd choice             → Lung scan (V/Q scan) Best investigation for PE                →  Chest CT with contrast (MDCTA) Most accurate investigation for PE  →  Invasive pulmonary angiography Gold - standard test for PE             →   Invasive pulmonary angiography Screening test for PE                    →  D-dimer assay