External Validation of the CHOD Risk Scale

Overview

Severe COVID-19 is associated with a hypercoagulable state, with a high risk of thrombotic phenomena such as pulmonary thromboembolism (PE). Its diagnostic suspicion is complicated, due to the overlap of symptoms of PE with those of COVID-19 itself. Therefore, it is essential to improve PE prediction to optimise the performance of confirmatory imaging tests such as thoracic CT angiography. Early diagnosis has relevant therapeutic implications, as it justifies starting anticoagulant treatment early, with a possible positive impact on the clinical evolution of these patients. The CHOD risk scale has recently been described: the acronym for C-reactive protein concentration, heart rate, oxygen saturation, and D-Dimer levels. Its initial description was carried out in a study in a single hospital centre. proving to be an easy-to-apply tool, useful for predicting the appearance of PE in patients hospitalized for COVID-19. The objective of this study is to carry out an external validation of this scale in patients hospitalized for COVID-19 pneumonia, through an observational, cross-sectional, multicenter, real-life study in patients hospitalized for severe COVID-19 pneumonia, confirmed by objective methods, and showing high D-dimer values. Imaging tests with CT angiography will be performed in patients with elevated D-Dimer, following international clinical practice regulations. Given that they will be consecutive patients, CT angiography will be performed in all patients regardless of the patient's clinical probability of PE as long as they meet the inclusion criteria and none of the exclusion criteria. To calculate the PE predictive power of the CHOD scale in the validation cohort, a methodology similar to that used in the construction cohort will be used, that is, the use of a ROC curve. Taking into account that a similar predictive value (with a maximum error of 5%) between the CHOD scale in the construction cohort and that of this study (validation cohort) will be considered as an adequate external validation, and taking into account a statistical power of 80%, an alpha error of 5% and a maximum loss of patients of 15%, the required sample size is 245 patients. Since 7 centres initially participate, each of which will have to contribute 35 valid consecutive patients for the analysis.