D-dimer in Adolescent Pulmonary Embolism

Abstract

Background: D-dimer is used to aid in diagnosing adult pulmonary embolism (PE). D-dimer has not been validated in adolescents. Clinicians must balance the risk of overtesting with that of a missed PE. D-dimer may be useful in this context. This study evaluates D-dimer in PE-positive and PE-negative adolescents.

Methods: PE-positive patients < 22 years were diagnosed with PE by computed tomography (CT) or high-probability ventilation/perfusion, seen at emergency departments (EDs)/hospitals within a 16-hospital system across two states, January 1998 through December 2016. Of the 189 PE-positive patients, 88 (46.5%) had a D-dimer and were matched 1:1 by age, sex, and race to patients suspected of PE but confirmed negative by CT angiogram.

Results: Ages of PE-positive patients ranged from 13 to 21 years, 64 (73%) were female, and 52 (60%) were Caucasian. Mean D-dimer was significantly higher (3,256 ng/mL, 95% confidence interval [CI] = 2,505-4,006 ng/mL) in PE-positive versus PE-negative patients (1,244 ng/mL, 95% CI = 493-1,995 ng/mL; p < 0.001). Mean D-dimer was higher in patients with massive or submassive PE (8,742 ng/mL, 95% CI = 5,994-11,491 ng/mL), followed by PE in central (4,795 ng/mL [95% CI = 3,465-6,125 ng/mL), lobar (3,758 ng/mL [95% CI = 1,841-5,676), and distal (2,327 ng/mL [95% CI = 1,273-3,381 ng/mL]) arteries. When comparing thresholds of positive D-dimer (≥500, ≥750, and ≥1,000 ng/mL), D-dimer had sensitivities of 90, 82, and 67% and specificities of 16, 53, and 67%, respectively. Negative predictive values were 61, 75, and 71% while positive likelihood ratios were 1.1, 1.8, and 2.2, respectively.

Conclusions: This study represents the largest available cohort of adolescent patients examining the diagnostic value of D-dimer for PE. Our results indicate that depending on the threshold selected, D-dimer can be a sensitive test for PE in adolescents and that discriminative value is higher for a cutoff of 750 ng/mL than that for 500 ng/mL. Prospective studies investigating the diagnostic value of D-dimer and a clinical decision rule for PE in pediatrics are needed.