Pulmonary embolism rule-out criteria reduces the need for CT pulmonary angiography in low-risk patients (PERC)

Reference

Freund Y, Cachanado M, Aubry A, et al. Effect of the pulmonary embolism rule-out criteria on subsequent thromboembolic events among low-risk emergency department patients. The PROPER randomized clinical trial. JAMA 2018;319(6):559-566.

Synopsis

The PERC decision rule is an 8-item set of clinical criteria, including arterial oxygen saturation of 94% or less, pulse rate of at least 100 per minute, patient age at least 50 years, unilateral leg swelling, hemoptysis, recent trauma or surgery, prior PE or deep vein thrombosis, and exogenous estrogen use. These investigators identified all consenting adults who presented to an emergency department with new-onset presence or worsening of shortness of breath or chest pain and a low clinical probability of PE (estimated by the treating physician as less than 15% probability). The patients (N = 962) were cluster-randomized (concealed allocation assignment) based on emergency department location to a control group or to an intervention group with a diagnostic work-up that included an initial calculation of the PERC score. Patients who scored zero had no additional work-up for PE. Patients with a PERC score above zero had a standard diagnostic work-up that included D-dimer testing, followed by CTPA if the D-dimer result was positive (based on age-adjusted thresholds). The control group received only the standard work-up without a preceding PERC calculation. The intervention strategy continued for 6 months, followed by a 2-month washout period, and then the 2 groups crossed-over to the other diagnostic strategy protocol. Individuals who assessed outcomes remained masked to group assignments. Follow-up occurred for 97% of patients at 3 months. Using both intention-to-treat and per-protocol analyses, there was no significant difference in the proportion of patients in the PERC group who were given an initial diagnosis of PE compared with patients in the control group (1.5% vs 2.7%). Only one PE (0.1%) was diagnosed during follow-up in the PERC group; none in the control group. CTPA occurred in significantly fewer patients in the PERC group thanin the control group (13% vs 23%; difference -10%; 95% CI -13% to -6%).