The authors of this paper randomized 18 EDs to either a protocol of intervention followed by control, or control followed by intervention. The study population included 726 patients in the intervention group and 688 in the control group.
The intervention strategy to rule out PE consisted of assessing the YEARS criteria and D-dimer testing. PE was ruled out in patients with no YEARS criteria and a D-dimer level below 1,000 ng/mL and in patients with one or more YEARS criteria and D-dimers below an age-adjusted threshold (defined as age times 10 ng/mL in patients aged 50 years and older).
The control strategy consisted of D-dimer testing for all patients with the threshold at age-adjusted levels; D-dimers about these levels prompted chest imaging.
Overall, the risk of a missed VTE at 3 months was noninferior between the groups (0.15% in the intervention group and 0.80% in the controls).
“The intervention was associated with a statistically significant reduction in chest imaging use,” the researchers wrote.
This study’s findings were limited by randomization at the center level, rather than the patient level, and the use of imaging on some patients despite negative D-dimer tests, the researchers wrote. However, their findings support those of previous studies and especially support the safety of the intervention, in an emergency medicine setting, as no PEs occurred in patients with a YEARS score of zero who underwent the intervention.
Downsides to applying algorithms to every patient explained
In anaccompanying the JAMA study, Marcel Levi, MD, and Nick van Es, MD, of Amsterdam University Medical Center, emphasized the challenges of diagnosing PE given that many patients present with nonspecific clinical manifestations and without typical signs and symptoms. High-resolution CT pulmonary angiography allows for a fast and easy diagnosis in an emergency setting. However, efforts are ongoing to develop alternative strategies that avoid unnecessary scanning for potential PE patients, many of whom have alternative diagnoses such as pulmonary infections, cardiac conditions, pleural disease, or musculoskeletal problems.
On review of the JAMA study using the YEARS rule with adjusted D-dimer thresholds, the editorialists noted that the data were robust and indicated a 10% reduction in chest imaging. They also emphasized the potential to overwhelm busy clinicians with more algorithms.
“Blindly applying algorithms to every patient may be less appropriate or even undesirable in specific situations in which deviation from the rules on clinical grounds is indicated,” but a complex imaging approach may be time consuming and challenging in the acute setting, and a simple algorithm may be safe and efficient in many cases, they wrote. “From a patient perspective, a negative diagnostic algorithm for pulmonary embolism does not diminish the physician’s obligation to consider other diagnoses that explain the symptoms, for which chest CT scans may still be needed and helpful.”
The Annals of Internal Medicine study was supported by the Dutch Research Council. The JAMA study was supported by the French Health Ministry. Dr. Stals, Dr. Freund, Dr. Pal, Dr. Levi, and Dr. van Es had no financial conflicts to disclose.