The epidemiological history is very important to diagnosis COVID-19, especially on early age. Guan et al. reported 1099 patients with laboratory-confirmed COVID-19 from 552 hospitals in 30 provinces, autonomous regions, and municipalities in China through January 29, 2020. They found 43.9% patients were residents of Wuhan. Among the cases who lived outside Wuhan, 72.3% had contact with residents of Wuhan . Fever, dry cough and fatigue are the most common presenting clinical symptoms of the COVID-19 infected cases. About 20% of patients are severe, and the mortality is nearly 3 % [6, 7].
Chest CT is a very important method to diagnose COVID-19. Typical CT imaging manifestation include: 1) quantity (often more lesions); 2) dominant distribution (mainly subpleural); 3) density (mostly uneven, a paving stones-like change mixed with ground glass density and interlobular septal thickening, etc.); 4) shape (large block, patchy, lumpy, nodular, honeycomblike or grid-like, cord-like, etc. Among of them, multiple, patchy, segmental or sub-segmental ground glass density shadows in bilateral lungs are the most common COVID-19 CT images. Some accompany by fine-grid or small honeycomb-like interlobular septa thickening. The high-resolution computed tomography (HRCT) shows the slightly high-density and ground-glass change with fuzzy edge in the fine-grid or small honeycomb-like thickening of interlobular septa. The thinner the chest CT scan layers, the clearer the above imaging manifestations are displayed . Accurate RNA detection of COVID-19 is a diagnostic method close to the gold standard and could be strongly recommended. The first case was a typical COVID-19 case and diagnosed easily on the basis of typical epidemiologic characteristics, typical clinical manifestations, typical chest images, and nucleic acid test.
Recently, the detection of COVID-19 nucleic acid used by RT-PCR has been found to have some shortcomings, as following:1) the nucleic acid detection technology develops immaturely; 2) patient viral load is low; 3) different manufacturers may lead to different detection rate; or 4) clinical sampling is improper. Fang et al.reported 51 COVID-19 cases, and they found that the diagnosis sensitivity using chest CT image was greater than that using nucleic acid test (98% vs 71%, p<.001).Tao et al summarized 1014 COVID-19 patients, and their study showed 59% (601/1014) of the cases had positive RT-PCR results, and 88% (888/1014) had positive chest CT results. The sensitivity of CT in suggesting COVID-19 was 97% based on positive RT-PCR results . In our study, the second case received COVID-19 nucleic acid test 7 times and the test results remained controversial. He was diagnosed with COVID-19 after 5 days, although his COVID-19 CT imaging manifestation was typical. On February 12, 2020, COVID-19 was firstly diagnosed clinically using chest CT in Hubei province according to “diagnosis and treatment of novel coronavirus pneumonia in China (The Fifth Edition, passed on February 5, 2020)”. A total of 13332 new cases in Hubei province were clinically confirmed using chest CT without nucleic acid test on one day and received timely treatment (Figure 3).