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Clinical and computed tomographic (CT) images characteristics in the patients with COVID-19 infection: What should radiologists need to know?

OBJECTIVE: To evaluate the clinical and computed tomographic (CT) features in the patients with COVID-19 pneumonia confirmed by the real-time reverse transcriptase polymerase chain reaction (rRT-PCR) amplification of the viral DNA from a sputum sample. MATERIAL AND METHODS: Clinical information and CT findings of a total of 14 patients with COVID-19 infection (age range, 12–83 years; females 6) were analyzed retrospectively. The clinical information includes the history of exposure, laboratory results, and the symptoms (such as fever, cough, headache, etc.); CT findings of chest include the extension and distribution of lesion, the ground-glass opacity (GGO), consolidation, bronchovascular enlarged, irregular linear appearances, pleural effusion, and lymphadenopathy. RESULTS: Eight patients had the exposure history for recent travel to Wuhan of Hubei province (8/14, 57%), 6 had the exposure to patients with COVID-19 infection. Significant statistical differences were observed in lymphocyte percentage decreased and C-reactive protein elevated (p = 0.015). Seven patients had fever, 7 had cough, 2 had headache, 3 had fatigue, 1 had body soreness, 3 had diarrhea, and 2 had no obvious symptoms. In chest CT examination, 10 patients were positive (10/14, 71.43%). Among these patients, 9 had lesions involving both lungs (9/10, 90%), 8 had lesions involving 4 to 5 lobes (8/10, 80%). Most of lesions were distributed peripherally and the most significant lesions were observed in the right lower lobe in 9 patients (9/10, 90%). Nodules were observed in 5 patients (5/10, 50%); GGO, consolidation, and bronchovascular enlarged were shown in 9 patients (9/10, 90%); irregular linear appearances were revealed in 7 patients (7/10, 70%); and pleural effusions were exhibited in 2 patients (2/10, 20%). Last, no patients showed lymphadenopathy. CONCLUSION: There were some typical CT features for diagnosis of COVID-19 pneumonia. The radiologists should know these CT findings and clinical information, which could help for accurate analysis in the patients with 2019 novel coronavirus infection.

before treatment. The days were also recorded for the patients with COVID-19 pneumonia from the onset of chief symptom to the first CT scan.

Diagnostic criteria for the patients with COVID-19 pneumonia
According to COVID-19 pneumonia diagnosis and treatment plan promulgated by National Health Commission of the People's Republic of China. Two steps in conclusion for diagnosis of COVID-19 are as following: The First Step -Diagnosis of the suspected cases: For this purpose, comprehensive analysis for epidemiological exposure history and clinical manifestations in diagnosis of COVID infection are performed. First, 4 epidemiological history are examined including (1) a history of travel or residence in Wuhan city and surrounding areas, or other communities with case reports within 14 days before the onset; (2) a history of contact with COVID-19 patients (nucleic acid test positive) within 14 days prior to onset; (3) a history of exposure to the patients with fever or respiratory symptoms from the city of Wuhan and its surrounding areas, or from the community with reported cases within 14 days before the onset; and (4) cluster onset. Next, 3 clinical manifestations are checked including (1) fever and/or respiratory symptoms; (2) with the COVID-19 imaging features; and (3) at the early stage, the total number of white blood cells was normal or decreased, and the count of lymphocytes decreased. In current clinical practice, patients with one of the following two conditions are considered suspected cases namely, (1) the patients who have any one of four aspects in the epidemiological history and any two of three aspects in the clinical manifestations, and (2) the patients who have no clear epidemiological history, but have three aspects of the clinical manifestations.
The Second Step -Confirmation of COVID-19 infected cases: The suspected cases with one of the following pathogenic evidences are confirmed as COVID-19 infected cases namely, (1) RT-PCR detection of new coronavirus nucleic acid is positive; and (2) the novel coronavirus is highly homologous to the COVID-19.

Evaluation of chest CT findings
When chest CT examination was over, all the CT images dataset were reconstructed at the workstation with filtered back projection algorithm based on its original dataset. CT images with 1 mm thickness and no intersection gap were generated for chest CT datasets. Multiplanar reformation (MPR) images (including axial, sagittal, coronal image) were also generated, and these images were subsequently loaded into picture archiving and communication system (PACS) workstation (Syngo.plaza, Siemens) for interpretation in consensus by two experienced radiologists (P.G.L. and J.J.M) with approximately 6 years and 20 years, respectively.
At first, the overall image quality of the patient with COVID-19 infection was evaluated: the overall image quality degree was scored as poor (score 1), suboptimal (score 2), diagnostic (score 3), superior (score 4), excellent (score 5). The image quality score ≥3 was considered as satisfaction for evaluation in clinical practice.

Statistical analysis
Statistical analysis was performed using SPSS software (version 23.0, SPSS Inc., Chicago, IL). Two groups of laboratory examination were classified according to the radiologic features of positive or negative chest CT results in the patients with COVID-19 infection. Fisher's exact test was used to compare laboratory indexes. P < 0.05 was considered statistically significant difference.

Evaluation of chest CT features
For subjective assessment of image quality in the patients with COVID-19 infection, the overall image quality was satisfactory for evaluating the CT features. Of 14 patients, 13 patients had an excellent score of image quality, one patient had superior score because of minimal movement artifact.

Discussion
In this study, the results we got suggested that fever and cough were the main clinical manifestations in the patients with COVID-19 infection; Headache, diarrhea, and body soreness were relatively rare. Especially, two patients with COVID-19 infection were without any significant symptoms. As for the chest CT findings, most of lesions distributed periphery or peribronchovascular in the lung parenchymal. GGO, bronchovascular enlarged, and consolidation were the common radiological characteristics in the chest CT examination. Therefore, knowing these features is essential, because early detection of the lesions in the patients with suspected COVID-19 and precise diagnosis could be helpful to patients' isolation and treatment (FIGURE 1), and to avoid containment of the health individuals or their families.
All of 14 patients had the exposure history of recently travel to Wuhan (8/14) or exposure to the patients with COVID-19 infection (6/14). Fever, cough, diarrhea, sore throat, nausea and vomit, fatigue, and no significant symptoms, etc. were observed in the patients with COVID-19 infection [13][14][15]. In our study, the main clinical manifestation was fever, and cough. Diarrhea as the chief symptom was also discovered in 3 cases. However, only two patients without any significant symptoms, negative CT Table 2 The Patients' Laboratory Examination Results

Measure of laboratory results
All data  Table 2 The Patients' Laboratory Examination Results

Measure of laboratory results
All data Note: "a" Make comparison between chest CT positive and negative cases for laboratory results elevated; "b" Make comparison between chest CT positive and negative cases for laboratory results decreased. Table 3 The  finding was observed in one of these two cases, and the other one with a nodular in the right lower lobe of chest CT examination.
Recently, literatures reported that GGO, consolidation, air bronchogram, and pleural effusion etc. were shown in the chest CT [6,13], and the pleural effusion or lymphadenophathy was rare [4,16]. The lesions distributed in pulmonary parenchyma were single lobe (10/24, 42%) or bilateral multi-lobes (10/24, 42%) in the stage-1 of COVID-19, single lobe (4/20, 20%) or bilateral multi-lobes (16/20, 80%) in the stage-4 [17]. In our study, the results revealed that GGO, bronchovascular enlarged in the lesions, linear appearances, and consolidations were found in the patients with COVID-19 pneumonia. The presence of pleural effusion was seen in two cases (Fig. 2). There was no case with lymphadenopathy. (8/10, 80%) patients with lesions involving 4 to 5 lobes distributed peripherally or subpleural regions, the most significant lesions were observed in the bilateral lower lobes, especially in the right lower lobe (9/10, 90%). Previous studies shown that the most frequency of lobe involvement was located in bilateral lower lobe [16,18,19], especially located in the right lower lobe [16,19,20]. Therefore, we speculated that involvement of lower lobes (the particular involvement of right lower lobe) were the relative specific sign for the radiologists to know in the patients with COVID-19 pneumonia (Fig. 3).  Generally, differential diagnosis for COVID-19 pneumonia includes virus pneumonia, fugal pneumonia, and bacterial pneumonia. The radiologic features of viral pneumonia are associated with the viral infectious pathogenesis. GGO and consolidation are the typical characteristics in most of the viral pneumonia. Not all of the viral pneumonia demonstrated with typical radiologic features because of the similar pathogenesis in the same viridae. However, recognizing the pneumonia patterns may aid doctor in reducing the unnecessary use of antibiotics. Therefore, the radiologic features of virus pneumonia are diverse and overlap [21]. Currently, definite diagnosis of COVID-19 infection cannot be achieved by using imaging features alone. Identification of the types of viral pathogens may not always be easy. As for the fungal pneumonia and bacterial pneumonia, consolidation plus nodules or consolidation plus GGO and nodules is suggested to diagnose for invasive fungal disease. Subsegmental or segmental consolidations are more frequent in bacterial pneumonia than in invasive fungal disease. Large nodules, as well as nodules with halo sign or both small and large nodules, are related to invasive fungal disease [22]. In addition, although rare enough, the perinodular halo is highly specific for invasive aspergillosis [23]. Therefore, identification of the types of viral pathogens may not always be easy by utilizing imaging characteristics alone. Radiologist should make diagnosis of COVID-19 by radiologic features in combination with clinical manifestation, exposure histology, and laboratory results.
The laboratory examination results suggested that the total number of white blood cells was normal in 14 patients (12/14, 86%). However, significant statistical differences were observed in lymphocyte percentage decreased and C-reactive protein elevated (all P = 0.015), and there were no significant statistical differences in the other laboratory examination results between positive and negative chest CT results in the patients with COVID-19 infection in our study. Previous studies shown that the total number of white blood cells was normal (590/978, 60%), the percentage of lymphocyte count was decreased (731/879, 83%), C-reactive protein was increased (481/793, 61%) [24]. Therefore, Knowing the clinical information is helpful for radiologists to diagnose COVID-19 pneumonia in the patients with suspected novel coronavirus infection (2019-nCoV), and the more details of the correlation between CT findings and laboratory examinations need to be further study.
This study also has several limitations. First, the sample size was small, especially the different stages of COVID-19, we just described the clinical manifestation, laboratory examination results, and chest CT features, further research would be conduct for statistical analysis if the sample is expanded. Second, some of laboratory indexes were not available from all the study subjects in this retrospective study. Third, the more details on the correlation between CT findings and laboratory examinations need to be further study to add information for diagnosis in the patients with suspected COVID-19 infection. Last, CT features were evaluated by two experienced radiologists in consensus, inter-observer agreement for two radiologists in overall image quality or CT features evaluation was not performed.

Conclusion
This study suggested that fever and cough were most frequent in the clinical characteristics in the patients with COVID-19 infection. Lymphocyte percentage decreased and C-reactive protein elevated may provide some information of laboratory findings to diagnose COVID-19 pneumonia. MSCT is a good tool to detect early and/or mild lesions of COVID-19 pneumonia. Multiple GGO, consolidation, and bronchovascular enlarged were common seen. Pleural effusion or lymphadenopathy was rare. Furthermore, the history of exposure is also an important clue to suspect those who may be infected current novel coronavirus. Therefore, the radiologists should know the key points of clinical manifestation, laboratory findings, and exposure history to diagnose the patients with suspected COVID-19 infection in clinical practice beyond radiologic findings.

Conflicts of interest
The authors have no potential conflicts of interest to disclose.