Age-adjusted cut-off using the IL D-dimer HS assay to exclude pulmonary embolism in patients presenting to emergency

The ADJUST-PE study showed that an age-adjusted D-dimer (AADD) (age years × 10 ng/mL if >50 years) combined with an unlikely pre-test probability (PTP) can increase the proportion of older patients in whom pulmonary embolism (PE) can be safely excluded, but the IL D-dimer HS assay was not assessed. To assess the ability of the IL D-dimer HS assay to exclude PE using the AADD.

Retrospective analysis of consecutive patients presenting with symptoms of acute PE to one of three Monash Health Emergency Departments (January 2013-January 2014) who had computed tomography pulmonary angiography. In the group with D-dimer, efficiency (proportion of PE excluded based on a combination of unlikely PTP and negative D-dimer) was determined using (i) current laboratory (200 ng/mL), (ii) conventional (230 ng/mL) and (iii) modified (375 ng/mL if age ≥60 years) AADD cut-offs.

A total of 176 patients with D-dimers was included (mean age = 58.5 years; 54.0% males; 71.0% age >50 years). Prevalence of PE in the overall, unlikely and likely PTP groups, was 17.0, 13.0 and 24.6% respectively. In the unlikely PTP group (115 patients), efficiency for the current, conventional, modified and AADD cut-offs was 9.6, 24.3, 30.4 and 37.4% respectively.

The absolute increase in efficiency of an AADD compared to conventional cut-off using the IL D-dimer HS assay is modest (~10%) and requires prospective validation. Modifying our cut-off to 230 ng/mL and systematic implementation of a clinical algorithm, including D-dimer testing and PTP, is likely a more important first step.