Effect of Using an Age-adjusted D-dimer to Assess for Pulmonary Embolism in Community Emergency Departments

Background: The objective of this study was to evaluate the effect of changing the laboratory-reported D-dimer reference intervals to age-adjusted reference intervals on the use of advanced chest imaging and 30-day adverse events among emergency department (ED) encounters.

Methods: A retrospective interrupted time-series analysis of ED encounters for patients > 50 years evaluated for suspected pulmonary embolism (PE) from April 2014 to April 2016. The primary outcome was use of advanced diagnostic imaging, and the secondary outcome was 30-day mortality or PE diagnosis. Secondary analyses also quantified delayed PE diagnoses pre- and postintervention. A generalized estimating equation segmented logistic regression model, adjusting for patient and facility characteristics, was used to determine changes in odds of diagnostic imaging and 30-day mortality or PE diagnoses.

Results: A total of 10,534 (5,153 pre- and 5,381 postimplementation) ED encounters were included. Advanced imaging was obtained in 35.9% of pre- versus 33% of postimplementation encounters. Age-adjusted D-dimer (AADD) showed a small and nonsignificant decrease in month-to-month trends of advanced chest imaging postimplementation (odds ratio [OR] = 0.98, 95% confidence interval [CI] = 0.96 to 1.00). Use of advanced imaging in patients with D-dimer values lower than 500 ng/mL fibrinogen-equivalent units (FEU) was similar in the preintervention (5.8%) and postintervention (6.8%) periods. However, imaging was obtained in 30% of patients postintervention with a D-dimer result less than AADD reference interval , but more than the historical 500 ng/mL FEU reference interval. Implementing an AADD threshold demonstrated no change in the rate of 30-day adverse events (missed PE or mortality).

Conclusion: Changing the laboratory-reported D-dimer reference intervals for evaluation of PE was not associated with reduction in advanced chest imaging and did not increase 30-day adverse events. However, there was substantial noncompliance with the age-adjusted reference intervals in the postintervention period likely blunting the impact of this intervention.