Pulmonary embolism rule-out criteria (PERC) rule in European patients with low implicit clinical probability (PERCEPIC): a multicentre, prospective, observational study.

Background: The ability of the pulmonary embolism rule-out criteria (PERC) to exclude pulmonary embolism without further testing remains debated outside the USA, especially in the population with suspected pulmonary embolism who have a high prevalence of the condition. Our main objective was to prospectively assess the predictive value of negative PERC to rule out pulmonary embolism among European patients with low implicit clinical probability.

Methods: We did a multicentre, prospective, observational study in 12 emergency departments in France and Belgium. We included consecutive patients aged 18 years or older with suspected pulmonary embolism. Patients were excluded if they had already been hospitalised for more than 2 days, had curative anticoagulant therapy in progress for more than 48 h, or had a diagnosis of thromboembolic disease documented before admission to emergency department. Physicians completed a standardised case report form comprising implicit clinical probability assessment (low, moderate, or high) and a list of risk factors including criteria of the PERC rule. They were asked to follow international recommendations for diagnostic strategy, masked to PERC assessment. The primary endpoint was the proportion of patients with low implicit clinical probability and negative PERC who had venous thromboembolic events, diagnosed during initial diagnostic work-up or during 3-month follow-up, as externally adjudicated by an independent committee masked to the PERC and clinical probability assessment. The upper limit of the 95% CI around the 3-month thromboembolic risk was set at 3%. We did all analyses by intention to treat, including all patients with complete follow-up. This trial is registered with ClinicalTrials.gov, number NCT02360540.

Findings: Between May 1, 2015, and April 30, 2016, 1773 consecutive patients with suspected pulmonary embolism were prospectively assessed for inclusion, of whom 1757 were included. 1052 (60%) patients were classed as having low clinical probability, 49 (4·7%, 95% CI 3·5-6·1) of whom had a venous thromboembolic event. In patients with a low implicit clinical probability, 337 (32%) patients had negative PERC, of whom four (1·2%; 95% CI 0·4-2·9) went on to have a pulmonary embolism.

Interpretation: In European patients with low implicit clinical probability, PERC can exclude pulmonary embolism with a low percentage of false-negative results. The results of our prospective, observational study allow and justify an implementation study of the PERC rule in Europe.

Funding: French Ministry of Health.