Investigation of age-adjusted D-dimer using an uncommon assay

Area of Science:

• Emergency Medicine
• Diagnostic Imaging
• Clinical Chemistry

Background:

• Age-adjusted D-dimer testing is recommended for evaluating acute pulmonary embolism (PE).
• Most research uses Fibrinogen Equivalent Units (FEU), with limited data on D-Dimer Units (D-DU).
• A novel age-adjustment formula for D-DU assays was developed to address limitations of existing methods.

Purpose of the Study:

• To retrospectively evaluate the test characteristics of a novel age-adjusted D-dimer formula using D-DU.
• To compare the novel formula against traditional and American College of Emergency Physicians (ACEP)-endorsed age-adjusted thresholds for acute PE evaluation in the ED.

Main Methods:

• Retrospective chart review of adult patients undergoing D-dimer testing and CT pulmonary angiography (CTPA).
• Inclusion criteria: D-dimer testing and CTPA imaging.
• Outcome measures: sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of different D-dimer thresholds.

Main Results:

• The novel age-adjusted D-dimer formula demonstrated a sensitivity of 97.0% and specificity of 27.9%.
• Traditional D-dimer cutoff showed 99.8% sensitivity and 16.7% specificity.
• The ACEP-endorsed formula yielded similar test characteristics to the novel formula.

Conclusions:

• Age-adjusted D-dimer testing with D-DU assays enhances specificity for acute PE evaluation in the ED.
• The novel age-adjusted formula and the ACEP-endorsed formula performed well, with the novel formula showing a trend towards improved characteristics.
• This approach maintains high sensitivity and NPV, aiding in appropriate patient selection for PE workup.