Background: Intermediate pulmonary embolism (PE) risk patients (Well’s Score 2-6) present a challenge to ED clinicians as the risk of starting unnecessary anticoagulants must be weighed against delayed time to treatment. Studies in inpatient populations demonstrated a relationship between D-dimer and PE location, with proximal clots associated with a higher D-dimer and increased mortality. We hypothesized this relationship would hold true in adult ED patients. Our goal was to determine a D-dimer cut-off that could help clinicians diagnose proximal PEs (lobar or main pulmonary artery). This decision making tool to stratify intermediate risk patients would be helpful when imaging is delayed or unavailable.
Methods: A retrospective chart review was performed on 1201 patients with a diagnosis of PE from 12 EDs in 2 states over the past 5 years. Locations of PE were based on largest occluded artery as noted by an attending radiologist and separated into 4 categories: No PE, Distal (segmental or sub-segmental arteries), Lobar, and Main. A Kruskal-Wallis with a Dunn All-Pairs nonparametric comparison was performed to determine significant differences between median D-dimers. ROC analysis was performed to determine D-dimer cut-offs to identify patients with proximal PEs.
Results: 305 patients met our inclusion criteria of adults (≥18) having a CT pulmonary angiogram (CTPA) and D-dimer performed within 24 hours of ED admission. Patients were excluded from the study if they had an active cancer, inconclusive CTPA reading, ongoing anticoagulation treatment, non-thrombotic emboli, coagulopathy, or were pregnant.
Median D-dimers [25th, 75th percentile] were: No PE [760 (600,1280)], Distal [1850 (1077, 3342)], Lobar [4990 (1975, 8850)], Main [7255 (4032, 12800)]. D-dimers were significantly different across all pairwise comparisons except Distal vs No PE. ROC analysis to identify proximal PEs had a maximum AUC of 0.921 at a D-dimer cut-off of 2270 (Sensitivity=86%, Specificity=85%).
Conclusion: D-dimers are correlated with PE location in adult ED patients, with proximal PEs yielding a higher D-dimer. A D-dimer cut-off of 2270 is sensitive and specific for identifying intermediate risk patients with proximal PEs. Predicting the location of a PE with a D-dimer can decrease time to treatment and facilitate decision making when imaging is unavailable or delayed.