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Objectives: Determine whether D-dimer concentration in the absence of imaging can differentiate patients that require anti-coagulation from patients who do not require anti-coagulation.Methods: Data was obtained retrospectively from 366 hemodynamically stable adult ED patients with suspected pulmonary embolism (PE). Patients were categorized by largest occluded artery and aggregated into: 'Require anti-coagulation' (main, lobar, and segmental PE), 'Does not require anti-coagulation' (sub-segmental and No PE), 'High risk of deterioration' (main and lobar PE), and 'Not high risk of deterioration' (segmental, sub-segmental, and No PE) groups. Wilcoxon rank-sum test was used for 2 sample comparisons of median D-dimer concentrations. Receiver operating characteristic (ROC) curve analysis was utilized to determine a D-dimer cut-off that could differentiate 'Require anti-coagulation' from 'Does not require anti-coagulation' and 'High risk of deterioration' from 'Low risk of deterioration' groups.Results: The 'Require anti-coagulation' group had a maximum area under the curve (AUC) of 0.92 at an age-adjusted D-dimer cut-off of 1540 with a specificity of 86% (95% CI, 81-91%), and sensitivity of 84% (79-90%). The 'High risk of deterioration' group had a maximum AUC of 0.93 at an age-adjusted D-dimer cut-off of 2500 with a specificity of 90% (85-93%) and sensitivity of 83% (77-90%).Conclusions: An age-adjusted D-dimer cut-off of 1540 ng/mL differentiates suspected PE patients requiring anti-coagulation from those not requiring anti-coagulation. A cut-off of 2500 differentiates those with high risk of clinical deterioration from those not at high risk of deterioration. When correlated with clinical outcomes, these cut-offs can provide an objective method for clinical decision making when imaging is unavailable. [ABSTRACT FROM AUTHOR]