[Rapid Diagnosis of COVID-19 in A Patient without A Positive History of Contact Who Presented with Severe Hypoxia：Case Report]

We report the case of an 85-year-old woman who was transported to our hospital by ambulance with progressively worsening dyspnea and hypoxia She had no history of contact with any patient with coronavirus disease 2019 (COVID-19) The peripheral arterial oxygen saturation level on a 10 L/min non-rebreather-type mask was as low as 80% Chest auscultation revealed coarse crackles After emergency intubation, it was surmised that the probability of heart failure was low because of the lack of pink, frothy sputum Bacterial pneumonia was also considered to be unlikely, as the sputum was not purulent Moreover, laboratory data revealed a normal white blood cell count (6,100/μL) and no elevation of the serum procalcitonin level (0 63 ng/mL), which were also consistent with the condition not likely to be a bacterial infection Pulmonary thromboembolism was ruled out by the presence of coarse crackles on chest auscultation and normal blood pressure Thereafter, the possibility of COVID-19 was considered and the patient was immediately isolated Two days later, the polymerase chain reaction test for COVID-19 returned positive There was no evidence of transmission of the virus to the healthcare personnel who had treated this patient, including the 6 with medium-risk exposure, during the 3-week period after the exposure In the COVID-19 pandemic era, rapid differential diagnosis of hypoxia is essential to prevent further transmission of SARS-CoV-2 infection Our case highlights the importance of the sputum appearance/characteristics and laboratory data for rapidly ruling out diseases other than COVID-19