No PERC, Wells, Geneva – Just D-Dimers for Everyone?

July 12, 2024

Written by Laura Murphy

Spoon Feed
A “D-dimer only” pathway in patients with suspected pulmonary embolism (PE) was safely used to determine need for imaging without clinical decision rules, but there are some concerns with this approach.

Is simpler better?
This was a prospective multicenter implementation study in 2 Canadian EDs (between November 2019 and June 2021) of a D-Dimer focused clinical pathway for PE testing. A total of 16,155 patients (33.4% postimplementation, 30.7% preimplementation, 35.9% external control site) were tested for PE. The intervention was a PE testing bundle where all patients with suspected PE underwent D-dimer testing and automatic imaging (CTPA or ventilation-perfusion scan) if D-dimer result was ≥500 ng/mL. PE was ruled out if D dimer was <500 ng/mL or negative imaging. They looked at three primary outcomes:

• Implementation: proportion of patients tested in adherence with the pathway
• Clinical Benefit: proportion of patients who received pulmonary imaging
• Safety: diagnosis of PE within 30 days following negative PE testing.

Historical control was the pre-implementation period between January 2018 and October 2019, and external control was a third emergency department (within 2 miles of the other sites) within the same hospital system. There was excellent adherence to the protocol (97.6%), and the protocol was safe, 0.04% diagnosed with PE within 30 days (95%CI 0.01 to 0.16%). However, there was no effect on the proportion of patients undergoing PE imaging, though imaging yield increased post-implementation (aOR 4.89, 95%CI 1.17 to 20.53).

Implementation was associated with increased D-dimer use at intervention sites compared to control, but was also associated with higher imaging yield and increased PE diagnoses (aOR for PE prevalence 3.57, 95%CI 1.54 to 8.24). Whether or not these were clinically significant PE is unclear.

The authors justified the use of a simplified pathway rather than use of prediction scores or alternative testing pathways (such as age-adjusted D-dimer), and acknowledged that these validated pathways are more efficient in reducing chest imaging. The study was not powered to determine a difference in safety before and after intervention.

No patients with D-dimer <500 ng/mL were diagnosed with PE within 30 days. On the one hand, this suggests that use of D-dimer testing for patients regardless of risk is reasonable and safe. However, I wonder if use of this strategy may lead to over-testing of low risk patients (i.e. PERC-negative patients).

How will this change my practice?
I don’t think it will. While safe, this pathway did not decrease use of imaging to diagnose PE, and I’m not sure results are compelling enough for me to abandon other well-validated algorithms in favor of this simplified one.

Source
Implementation, Clinical Benefit and Safety of a D-Dimer-Focused Pulmonary Embolism Testing Pathway in the Emergency Department. Ann Emerg Med. 2024 Apr 23:S0196-0644(24)00156-2. doi: 10.1016/j.annemergmed.2024.03.010. Epub ahead of print. PMID: 38661619.