What are the tests for pulmonary embolus?

PE testing. If your history is strongly suggestive that you might have a pulmonary embolism-pe, then a blood test called a d-dimer might be ordered. If that is low, you don't have a clot. If high, the gold standard of testing for a pe is a spiral cat scan of the lungs with infusion. Ventilation-perfusion scans and pulmonary angiography are done infrequently these days as long as a ct scan can be done.
Several. The gold standard is a CT angiogram. If your kidney's aren't functioning well, you could get a V/Q scan. If that's not available, one could get an echocardiogram and if there's right ventricular enlargement and a dilated inferior vena cava, then that is concerning for PE.
Difficult diagnosis. The first step in diagnosing pulmonary embolus is clinical suspicion. Investigations may include chest x-ray and ct scan, d-dimer lab tests, ventilation and perfusion scan and rarely angiography.