Elevation of the D-dimer cut-off level might be applicable to rule out pulmonary embolism for active cancer patients in the emergency department.

Recent guidelines for diagnosing acute pulmonary embolism (PE) are based on clinical decision rules and D-dimer. D-dimer measurement is recommended only for patients who are 'PE-unlikely'. We aimed to assess the current guidelines for cancer patients and to determine an optimal D-dimer cut-off level. This retrospective observational study was conducted in the emergency department of Asan Medical Center (Seoul, Korea) between 02/2017 and 09/2017 for the development cohort and between 06/2018 and 02/2019 for the validation cohort. Among adult active cancer patients with suspected PE, we included those who were 'PE-unlikely' according to Wells' criteria and who underwent D-dimer testing and computed tomographic pulmonary angiography (CTPA). A total of 498 patients (227 in the development cohort and 271 in the validation cohort) were included, and PE was diagnosed in 8.8% and 18.5% of patients, respectively. The optimal D-dimer cut-off level was 2.0 μg/mL. This elevated cut-off level showed a much higher specificity of 21.3% (95% confidence interval [CI] 16.2-27.3%) and 21.7% (95% CI 16.8-7.6%) in the development and validation sets, respectively, compared with the specificity of 4.4% (95% CI 2.3-8.1%) and 4.1% (95% CI 2.2-7.6%) using the age-adjusted cut-off. The new D-dimer cut-off value identified unnecessary CTPA for 21.3% of patients (absolute difference, 16.9%, 35 of 207) in the development cohort and 21.7% (absolute difference, 17.6%, 39 of 221) of patients in the validation cohort compared to using the standard age-adjusted cut-off. The elevated D-dimer cut-off value combined with Wells' criteria might reduce unnecessary CTPA in active cancer patients with a 'PE-unlikely' classification. Further clinical trials are warranted to improve the PE diagnostic strategy in cancer patients.