External validation of the PEGED diagnostic algorithm for suspected pulmonary embolism in an independent cohort

Sequential diagnostic algorithms are used in case of suspected pulmonary embolism (PE). The PEGeD study proposed a new diagnostic strategy to reduce the use of computed tomography pulmonary angiography (CTPA). We aimed to externally validate this diagnostic strategy in an independent cohort. We analyzed data from three prospective studies of outpatients with suspected PE. As per the PEGeD algorithm, patients were classified as having a low, moderate or high clinical pre-test probability (C-PTP). PE was excluded with a D-dimer < 1000 ng/mL in case of low C-PTP and < 500 ng/mL in case of moderate C-PTP. We assessed the yield and safety of this approach compared to previously validated algorithms. Among the 3308 evaluated patients, 1615 (49%) patients could have had PE excluded according to the PEGeD algorithm, without the need for imaging. Of these patients, 38 (2.3%; 95% CI 1.7 - 3.2) were diagnosed with a symptomatic PE at initial testing or during the 3 month follow-up. On further analysis, 36 patients out of these 38 patients had a positive age-adjusted D-dimer. The risk of VTE among the 414 patients with a D-dimer below 1000 ng/mL but above the age-adjusted D-dimer cutoff was 36/414 (8.7%; 95 % CI 6.4 - 11.8%). We provide external validation of the PEGeD algorithm in an independent cohort. Compared to standard algorithms, the PEGeD decreased the number of CTPA examinations. However, caution is required in patients with a low C-PTP and a D-dimer< 1000ng/mL but above their age-adjusted D-dimer cutoff.