SOURCE: van der Hulle, et al. Lancet 2017;390:289-297.

The consequences of missing pulmonary embolism (PE) are grave, and numerous prediction methods have evolved to refine our ability to properly identify PE. Unfortunately, increasing zeal for early identification of PE also has led to increased proportions of screened patients turning out to be PE-negative. Indeed, diagnostic imaging with CT pulmonary angiography (CTPA), the test of choice for PE confirmation, is negative in as many as 90% of patients suspected of PE.

CTPA is not without risk, both the immediate risk of contrast medium and concerns about long-term radiation consequences. You may be surprised to learn that the radiation of CTPA is equivalent to literally 1,500 chest X-rays, so it is not to be undertaken lightly.

A new decision rule considered by van der Hulle et al includes three primary items: clinical signs of deep vein thrombosis, hemoptysis, and clinical suspicion that PE is the most likely diagnosis. When coupled with D-dimer thresholds, this decision rule appears to reduce the frequency with which unnecessary CTPA is required. For instance, when none of the three primary items are present and d-Dimer is < 1,000 ng/mL, or when one to two primary items exist but D-dimer is < 500 ng/mL, PE is essentially excluded, and CTPA is not necessary. Compared with the widely used Wells’ rule, employment of this decision rule resulted in a significant diminution of the need for CTPA.

This large clinical trial (n = 3,465) of patients with potential PE, all of whom underwent CTPA to confirm the exclusionary capacity of the new diagnostic scheme, suggests that we may be able to be more efficient in limiting the number of patients who undergo CTPA.