Roy PM, Friou E, Germeau B, et al. - In view of the concerns regarding the overuse of diagnostic imaging among patients with suspected pulmonary embolism (PE), researchers sought to derive and validate a 4-level pretest probability rule (4-Level Pulmonary Embolism Clinical Probability Score [4PEPS]) that allows ruling out of PE solely on clinical criteria and optimized D-dimer measurement to safely reduce imaging testing for suspected PE. Databases from 3 merged management studies (n = 11,114; overall prevalence of PE, 11%) were used to perform derivation and internal validation of 4PEPS. Thirteen clinical variables scored from −2 to 5 were included in the 4PEPS. It results in the following strategy: (1) probability of PE was very low in cases with 4PEPS less than 0: PE ruled out without testing; (2) in cases with 4PEPS 0 to 5, there was low probability of PE: PE ruled out if D-dimer level is less than 1.0 μg/mL; (3) probability of PE is moderate in cases with 4PEPS 6 to 12: PE ruled out if D-dimer level is less than the age-adjusted cutoff value; (4) probability of PE is high if 4PEPS is greater than 12: PE ruled out by imaging without preceding D-dimer test. The 4PEPS strategy was confirmed to be safe and efficacious in 2 external validation cohorts (false-negative rates: 0.71% and 0.89%; absolute reductions in imaging testing: −19% and −22%, respectively). Overall, the 4PEPS strategy may result in a substantial and safe decrease in imaging testing for patients with suspected pulmonary embolism.