Context

A Bayesian combination of pretest probability assessment and D-dimer testing to rule out pulmonary embolism (PE) has been extensively validated in secondary care settings such as emergency departments. If this approach is shown to be safe in primary care settings, point-of-care D-dimer assays could allow physicians to rule out PE without referring patients to secondary care.

Patients who present to primary care are different than those who present to secondary care. Whereas patients who seek emergency care do so because of the sudden onset of distressing symptoms, primary care patients typically have more indolent presentations. Clinical prediction rules (eg, Wells score) may perform less well when symptoms are subtle and subacute. Similarly, since the release of D-dimer trails off as emboli dissolve and are …