AIM: One-third of PE imaging in ED may be avoidable

CTA showing pulmonary embolus in 48-year-old man. Source: Radiology 2012; 263: 271-8

Researchers have identified a performance gap related to adherence to a National Quality Forum (NQF) performance measure for appropriateness of CT pulmonary angiography in emergency department (ED) patients with a low pre-test probability of pulmonary embolism (PE), according to a study published online June 4 in Archives of Internal Medicine.

Existing clinical decision rules allow clinicians to safely exclude PE without imaging. However, adherence to these rules has been poor, which suggests a potential case of imaging overuse.

In 2011, the National Quality Forum (NQF) endorsed an imaging quality measure directed at appropriate use of CT in ED patients with low-probability of PE. NQF used retrospective data to estimate that 7 to 25 percent of imaging studies are avoidable.

Arjun K. Venkatesh, MD, MBA, of Brigham and Women’s Hospital in Boston, and colleagues designed a prospective, multicenter observational study of patients evaluated for PE from 2004 to 2007 at 11 U.S. EDs.

The study population included 5,940 patients, and 4,113 had low pre-test probability of PE. Venkatesh et al reported imaging was performed in 38 percent of low-risk patients. Among this group of 2,238 patients, 811 had no D-dimer testing and 394 had negative D-dimer results.

According to the NQF measure, imaging was avoidable in 32 percent of these patients. “Assuming 100 percent imaging specificity, measure adherence would have resulted in 11 'missed' PEs: eight patients with a negative D-dimer test result and three patients who would have undergone D-dimer testing [93 percent sensitivity] according to the guideline,” the authors wrote.

Venkatesh and colleagues offered several reasons for the failure to perform D-dimer testing. These included physician bias toward more “definitive” testing with CTPA (CT pulmonary angiography), use of CTPA to evaluate possible non-PE diagnoses, overestimation of expected D-dimer testing false-positivity, and underestimation of D-dimer testing sensitivity.

The researchers applied a multivariate model, which identified patient-level predictors of avoidable imaging: older age and inactive cancer. This relative dearth of patient-level predictors of avoidable imaging suggested probable links to variations in physician-level risk intolerance, patient preference or hospital characteristics not measured in the current study, according to the researchers.

Venkatesh and colleagues concluded, “The opportunity for improving the efficiency of imaging for suspected PE is large. Future work should focus on interventions to close this performance gap.”