External validation of the CHEDDAR score for suspected pulmonary embolism in patients with SARS-CoV-2 infection in an independent cohort

The accuracy of the classic scores that help stratify the pretest clinical probability of pulmonary embolism (PE) in SARS-CoV-2 infection (COVID-19) is low. Therefore, to estimate the risk of PE in these patients, a new set of guidelines must be established. The recently published CHEDDAR score proposes a new diagnostic strategy to reduce the use of computed tomography pulmonary angiography (CTPA) in non-critically ill SARS-COV-2 patients with suspected PE. According to the nomogram, patients are segregated into low-risk (< 182 points) or high-risk (>= 182 points) based on the best cut-off value to discard PE in the original cohort. We aimed to externally validate this diagnostic strategy in an independent cohort. We analyzed data from two retrospective cohorts of hospitalized non-critically ill COVID-19 patients who underwent a CTPA due to suspicion for PE. CHEDDAR score was applied. As per the CHEDDAR nomogram, patients were classified as having a low or high clinical pre-test probability. Of the 270 patients included, 69 (25.5%) had PE. Applying the CHEDDAR score, 182 (67.4%) patients could have had PE excluded without imaging. Among 58 patients classified as having high clinical pre-test probability, 39 (67.2%) had PE. Sensitivity, specificity, positive and negative predictive values, and AUC were 56%, 90%, 67%, 85%, and 0.783 (95% CI 0.71-0.85), respectively. We provide external validation of the CHEDDAR score in an independent cohort. Even though the CHEDDAR score showed good discrimination capacity, caution is required in patients classified as having low clinical pre-test probability with a D-dimer value > 3000 ng/mL, and a RALE score >= 4.