Can implementation of the pulmonary embolism rule-out criteria (PERC) safely reduce D-dimer and CTPA requests in a two-tier Wells model?

Introduction: An elevated D-dimer results in an extensive pulmonary embolism (PE) workup, subjecting patients to radiation, potentially harmful side effects from IV contrast and anticoagulation treatment. The PERC rule1 was developed to risk stratify low-risk patients (Wells score ≤2). If PERC score is 0, the pre-test probability would be so low that the risks involved in a PE workup outweigh the benefits1. This is yet to be tested in a two-tier Wells model (Wells score ≤4). Purpose: To assess the role of the PERC rule in safely reducing D-dimer and CTPA requests in a two-tier Wells model. Methods: We performed a retrospective analysis by applying the PERC rule in Wells score ≤4 patients who had a D-dimer test upon presentation to the Emergency Department of Royal Gwent Hospital, from July 2018 to December 2018. Results: 430 patients were included in this study. 141 patients had PERC=0. 27 of the PERC=0 patients had a CTPA scan and amongst those, 2 patients had confirmed PE. Our pre-test probability of PE in PERC=0 patients is 1.4%. By implementing the PERC rule, we could reduce the number of D-dimers ordered by 32.3% and CTPAs by 21.0%. Conclusion: Our pre-test probability of PE in patients with PERC=0 is 1.4%, below the recommended threshold of 1.8% (p=0.367)1. The use of the PERC rule could improve the use of CTPA in the diagnosis of PE. Reference: 1. Kline J, Mitchell A, Kabrhel C, Richman P, Courtney D. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. Journal of Thrombosis and Haemostasis. 2004;2(8):1247-1255.