EXTERNAL VALIDATION OF THE CAPAD SCORE TO PREDICT THE OCCURRENCE OF PNEUMOTHORAX AFTER CT-GUIDED PERCUTANEOUS TRANSTHORACIC LUNG BIOPSY

<bold>Background:</bold> The most common complication preventing outpatient management after percutaneous CT-guided lung biopsy (PTLB) is the occurrence of pneumothorax requiring chest tube placement. We previously developed a pragmatic score to predict the risk of clinically relevant pneumothorax after PTLB (hereafter called the CAPAD score), to guide patient management. <bold>Objectives:</bold> To perform external validation in an independent prospective validation cohort, of the ability of the CAPAD score to predict pneumothorax after PTLB. <bold>Method:</bold> Patients who underwent PTLB at the University Hospital Bichat-Claude Bernard (Paris, France) between January 1st 2015 and December 31st 2017 were prospectively evaluated for clinical and radiological factors potentially related to pneumothorax occurrence. The CAPAD score uses 5 variables to predict pneumothorax occurrence, namely: COPD, Anterior PTLB approach, >1 crossing through the Pleura, Aerial effusion ≥10 mm on the CT-scan performed at the end of the procedure, and skin-pleura Distance ≤30mm. <bold>Results:</bold> The CAPAD score could be calculated in 313 patients. Pneumothorax occurred in 95 patients (30.4 %). In this external cohort, with a cut-off value of 73 points, the score had a C-index of 0.77, sensitivity of 75% and specificity of 56%. The negative and positive predictive values were 84% and 43%, respectively. A score <73 was significantly associated with reduced need for chest tube insertion (2.0% in subjects with score <73 vs 12.0% if ≥73, p = 0.002). <bold>Conclusion:</bold> Our pragmatic CAPAD score demonstrated a good prognostic performance for predicting the risk of clinically relevant pneumothorax after PTLB.