A nurse practitioner suspects a pulmonary embolus in a 40-year-old patient. What test should be performed next?

Helical CT pulmonary angiography is the preferred test when a pulmonary embolism (PE) is suspected, particularly in an adult patient presenting with signs and symptoms indicative of this condition, such as sudden onset shortness of breath, chest pain, or hemoptysis. This imaging modality is highly sensitive and specific for detecting blood clots in the pulmonary arteries. It allows for rapid diagnosis and timely initiation of appropriate treatment, which is crucial given the potentially life-threatening nature of a PE.

When considering the other options, spirometry is primarily used to assess lung function and would not provide information specific to the presence of a pulmonary embolism. MRI, while useful in certain circumstances like visualizing soft tissue, is not commonly utilized for the diagnosis of PE due to its lower availability and longer duration for scanning compared to CT. Contrast venography, although it can detect deep vein thrombosis (DVT)—which can lead to PE—is more invasive and less commonly performed for diagnosis of PE when compared to helical CT pulmonary angiography. Thus, in the context of suspected pulmonary embolism, helical CT pulmonary angiography is the most appropriate next step in diagnostic evaluation.