Background: We aimed to develop and externally validate a novel machine learning model that can classify CT image findings as positive or negative for SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR).Methods: We used 2,928 images from a wide variety of case-control type data sources for the development and internal validation of the machine learning model. A total of 633 COVID-19 cases and 2,295 non-COVID-19 cases were included in the study. We randomly divided cases into training and tuning sets at a ratio of 8:2. For external validation, we used 893 images from 740 consecutive patients at 11 acute care hospitals suspected of having COVID-19 at the time of diagnosis. The dataset included 343 COVID-19 patients. The reference standard was RT-PCR.Results: In external validation, the sensitivity and specificity of the model were 0.869 and 0.432, at the low-level cutoff, 0.724 and 0.721, at the high-level cutoff. Area under the receiver operating characteristic was 0.76.Conclusions: Our machine learning model exhibited a high sensitivity in external validation datasets and may assist physicians to rule out COVID-19 diagnosis in a timely manner at emergency departments. Further studies are warranted to improve model specificity.
Coronavirus disease 2019 (COVID-19) has been recognized as a worldwide pandemic. However, the clinical course of COVID-19 remains poorly characterized. Although some cases of pneumothorax have been reported, they all had pulmonary complications or were managed with mechanical ventilation. We herein report a case of pneumothorax that developed even though the patient had no pulmonary underlying diseases and had never been managed with mechanical ventilation. In the present case, a lung bulla was found on chest computed tomography during treatment for COVID-19. We concluded that COVID-19 affected the formation of the lung bulla and induced the complication of pneumothorax.