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Chest CT imaging features and clinical outcome of coronavirus disease 2019 (COVID-19): A single-center case study in Ningbo, China

      Highlights

      • The most common CT features of COVID-19 are bilateral and peripheral GGOs with mixed consolidations or not in the lungs.
      • The chest CT findings are similar for patients with COVID-19, although they come from different sources of infection.
      • Chest CT plays an important role in the diagnosis and monitoring treatment response of COVID-19.
      • The diagnosis of COVID-19 should integrate clinical characteristics and CT features when RT-PCR test is negative.

      Abstract

      Objective

      The purpose of this study was to investigate the chest CT imaging features and clinical outcome of coronavirus disease 2019 (COVID-19) in Ningbo, China.

      Methods

      In this retrospective study, twenty-eight confirmed and seven highly suspected cases of COVID-19 were enrolled in Ningbo first hospital from January 26, 2020 to March 5, 2020. Cases were confirmed by real-time polymerase chain reaction (RT-PCR). The initial and follow-up chest CT imaging features, epidemiological history, and outcome were analyzed.

      Results

      The average age of the patients was 57.3 ± 15.3 years (range: 27–96 years), including 25 females and 10 males. On CT images, 89.3% (25/28) confirmed and 100% (7/7) suspected patients had ground-glass opacities (GGOs), and GGOs with mixed consolidations were observed in 35.7% (10/28) confirmed and 42.9% (3/7) suspected cases, most of these lesions were distributed under the peripheral of both lungs. 17 confirmed and 4 suspected cases had a history of participating in Ningbo Tian-tong Temple rituals and all had GGOs in their lungs during the initial CT scan. As of March 25, 2020, the lung lesions of our cases were significantly resolved and all patients have been discharged from the hospital.

      Conclusion

      The most common chest CT features are multiple bilateral and peripheral GGOs with mixed consolidations or not in the lungs of patients with COVID-19. Chest CT plays an important role in the diagnosis and monitoring treatment response of this disease. There was no reported death in our cases.

      Keywords

      1. Introduction

      Since December 2019, a cluster of patients with respiratory illness of unknown origin has emerged in Wuhan, Hubei province, China [
      • Lu H.
      • Stratton C.W.
      • Tang Y.W.
      Outbreak of pneumonia of unknown etiology in Wuhan, China: the mystery and the miracle.
      ]. The confirmed cases were caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2), infection, officially named coronavirus disease 2019 (COVID-19). It is a disease of person-to-person transmission [
      • Chan J.F.
      • Yuan S.
      • Kok K.H.
      • et al.
      A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster.
      ]. Up to March 4, 2020, China reported a total of 80,270 confirmed cases, 520 suspected cases, 49,856 cured cases and 2981 deaths []. At present, the disease has been spreading rapidly to >100 countries and 6 continents, leading to a serious global public health issue [
      • Patel A.
      • Jernigan D.B.
      nCo VCDCRT initial public health response and interim clinical guidance for the 2019 novel coronavirus outbreak-United States, December 31, 2019–February 4, 2020.
      ,
      • Ryu S.
      • Chun B.C.
      • Korean Society of Epidemiology-nCo VTFT
      An interim review of the epidemiological characteristics of 2019 novel coronavirus.
      ].
      The diagnosis of COVID-19 pneumonia is dependent on the epidemiological history, clinical manifestations, chest CT findings and viral nucleic acid detection by real time polymerase chain reaction (RT-PCR). At first, the confirmed cases were almost related to Huanan seafood market in Wuhan, China [
      • Huang C.
      • Wang Y.
      • Li X.
      • et al.
      Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China.
      ]. Later, numerous cases have been reported to have direct or indirect close contact with individuals of COVID-19 infection from Wuhan or other infected areas [
      • Xu X.W.
      • Wu X.X.
      • Jiang X.G.
      • et al.
      Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2) outside of Wuhan, China: retrospective case series.
      ]. Most of the patients with COVID-19 pneumonia have clinical symptoms of fever, cough, shortness of breath and so on [
      • Chen N.
      • Zhou M.
      • Dong X.
      • et al.
      Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study.
      ]. Chest CT plays a critical role in the diagnosis of the disease and the typical imaging findings were multi-focal ground-glass opacifications at the bilateral peripheral margin, mainly involving the lower right lobe [
      • Shi H.
      • Han X.
      • Jiang N.
      • et al.
      Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: a descriptive study.
      ]. RT-PCR test remains the reference standard method for diagnosis of COVID-19 even though with a lower sensitivity (59%) compared to chest CT imaging (88%) [
      • Ai T.
      • Yang Z.
      • Hou H.
      • et al.
      Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases.
      ]. However, the epidemiological characteristics, clinical and imaging manifestations, and outcome were not the same in different areas [
      • Xu X.W.
      • Wu X.X.
      • Jiang X.G.
      • et al.
      Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2) outside of Wuhan, China: retrospective case series.
      ,
      • Lillie P.J.
      • Samson A.
      • Li A.
      • et al.
      Novel coronavirus disease (Covid-19): the first two patients in the UK with person to person transmission.
      ].
      To date, only limited case studies have reported about the chest CT findings of COVID-19 and its temporal changes and relationship with clinical features [
      • Ai T.
      • Yang Z.
      • Hou H.
      • et al.
      Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases.
      ,
      • Wu J.
      • Wu X.
      • Zeng W.
      • et al.
      Chest CT findings in patients with corona virus disease 2019 and its relationship with clinical features.
      ]. Therefore, the purpose of this study was to explore the chest CT imaging features and clinical outcome for patients with COVID-19.

      2. Materials and methods

      2.1 Patients

      This study was approved by the Institutional Review Board of Ningbo First Hospital, Ningbo, Zhejiang province, China. Informed consent was waived for the nature of this retrospective study that involved no potential interest and/or risks between the patients and researchers. All of the data was evaluated with de-identified.
      A total of 28 confirmed and 7 suspected patients with COVID-19 who underwent chest CT scans in our hospital were enrolled in this study from January 26, 2020 to March 5, 2020. The following items were investigated in all patients: epidemiological history (travel and/or resident in Wuhan or close contact history to fevered persons who were confirmed or suspected with COVID-19 pneumonia within 14 days before the onset of illness), clinical manifestations (any symptoms of fever, cough, shortness of breath, muscle ache, fatigue, diarrhea, vomit, and etc.), chest CT imaging features (such as ground-glass opacity, consolidation, and etc.), laboratory examinations (blood routine test, and etc.) and RT-PCR test for COVID-19 nucleic acid in throat swabs or lower respiratory tract. The confirmed and highly suspected cases with COVID-19 pneumonia were treated in the isolation ward. All patients were excluded form type A (H1N1, H3N2, H7N9) and B influenza viruses infection by laboratory tests.
      According to the protocols from the national health commission of the people's republic of China, the discharged criteria were: afebrile for >3 days, respiratory symptoms improved significantly, lung lesions on chest radiograph or CT were significantly resolved, and at least two consecutive negative of COVID-19 nucleic acid tests with an interval of 24 h or more [
      • National Health Commission of the People's Republic of China
      Diagnosis and treatment protocols of pneumonia caused by a novel coronavirus (trial version 7, Chinese).
      ].

      2.2 Imaging acquisition and evaluation

      All patients were imaged with 5 mm slice thickness CT on a 16-row multidetector CT scanner (Siemens Somatom Sensation, Siemens, Erlangen, Germany) using the routine chest protocol. The patients were scanned by our technicians in a supine position, arm raised, during breath-holding at full inspiration. All CT images were evaluated using a lung window, with a window level of −600 HU and window width of 1400 HU. The slice thickness for reconstruction was 1.5 mm.
      Two radiologists with >20 years of experience (XZ. R and YF. T) analyzed all chest CT images independently and comparatively frame by frame and reached a consensus. The following imaging features on viral pneumonia were fully evaluated according to international standard nomenclature which were defined by the Fleischner Society and related literatures [
      • Hansell D.M.
      • Bankier A.A.
      • Mac Mahon H.
      • et al.
      Fleischner Society: glossary of terms for thoracic imaging.
      ,
      • Schoen K.
      • Horvat N.
      • Guerreiro N.F.C.
      • et al.
      Spectrum of clinical and radiographic findings in patients with diagnosis of H1N1 and correlation with clinical severity.
      ], including ground glass opacity (GGO), consolidation, bronchial wall thickening, interlobular septal thickening, and etc.

      2.3 Statistical analysis

      The variables were expressed as the mean ± standard deviation. The statistical comparison in different groups was analyzed by Chi-squared test. The results of the difference between the comparative tests were considered statistically significant at a 2-tailed value of p < 0.05. SPSS version 13.0 software (SPSS Inc., Chicago, IL) was used for all statistical analysis.

      3. Results

      3.1 Patient characteristics

      The clinical characteristics were summarized in Table 1. A total of 35 cases were enrolled in this study, including 10 males and 25 females, with an average of 57.3 ± 15.3 years (range: 27–96 years). Twenty-eight cases were confirmed to have COVID-19 pneumonia by RT-PCR and 7 suspected cases were negative in at least three times of RT-PCR tests for COVID-19 (each test interval was >24 h).
      Table 1Patient characteristics.
      VariablesValue
      Sex
       Male10 (28.6%)
       Female25 (71.4%)
      Age
       Mean57.3
       Standard deviation15.3
       Range27–96
      Exposure history
       Exposure to infected patients outside Wuhan5 (14.3%)
       Attend to Ningbo Tian-tong temple rituals21 (60.0%)
       Exposure to infected patients from Wuhan7 (20.0%)
       Unknown exposure2 (5.7%)
      Symptoms
       Fever25 (71.4%)
       Cough23 (65.7%)
       Shortness of breath1 (2.9%)
       Muscle ache2 (5.7%)
       Fatigue2 (5.7%)
       Vomit2 (5.7%)
       Diarrhea5 (14.3%)
       No obvious symptoms1 (2.9%)
      Comorbidities
       Diabetes5 (14.3%)
       Heart disease4 (11.4%)
       Hypertension15 (42.9%)
       With known primary cancer3 (8.6%)
       Immune diseases2 (5.7%)
       Chronic obstructive pulmonary disease0 (0%)
      On admission, most cases had symptoms of fever (25/35, 71.4%) and cough (23/35, 65.7%), and other symptoms were included in Table 1. The comorbidities include hypertension (15/35, 42.9%), diabetes (5/35, 14.3%), heart disease (4/35, 11.4%), with known primary cancer (3/35, 8.6%) and immune disease (2/35, 5.7%). No patients had chronic obstructive pulmonary disease. Laboratory examination (Table 2) showed the majority of the patients had a decreased and normal level of white blood cell count (33/35, 94.3%) and lymphocyte count (35/35, 100%), and 68.6% (24/35) of the patients had an increased level of C protein reaction.
      Table 2Laboratory examination results of the 35 patients.
      VariablesAll cases28 confirmed cases7 suspected cases
      White blood cell count (×109/L)
       <3.57 (20%)6 (21.4%)1 (14.3%)
       3.5–9.526 (74.3%)20 (71.4%)6 (85.7%)
       >9.52 (5.7%)2 (7.1%)0 (0%)
      Lymphocyte count (×109/L)
       <1.113 (37.1%)10 (35.7%)3 (42.9%)
       1.1–3.222 (62.9%)18 (64.3%)4 (57.1%)
       >3.20 (0%)0 (0%)0 (0%)
      C reactive protein (mg/L)
       <411 (31.4%)11 (39.3%)0 (0%)
       >424 (68.6%)17 (60.7%)7 (100%)
      Reference range: white blood cell count: (3.5–9.5) × 109/L; lymphocyte count: (1.1–3.2) × 109/L; C reactive protein: (0–4) mg/L.
      Epidemiological history revealed that 60.0% (21/35) of the cases had a close contact with a confirmed patient at a ritual in Ningbo Tian-tong Temple. Seven cases had a history of exposure to infected patients from Wuhan and 5 with infected patients outside Wuhan, and the remaining 2 had no obvious exposure history to patients with COVID-19. As of March 25, 2020, all cases were discharged from the hospital, including the 96-year-old female patient. During follow-up, there was no reported death.

      3.2 Chest CT imaging features and temporal changes

      A total of 110 chest CT scans were performed in 35 patients, 2–5 times per patient, with an average interval of 5.6 ± 2.8 days (range: 1–20 days). The initial chest CT scans were performed at 6.1 ± 3.7 days (range: 1–16 days) after the onset illness. The chest CT imaging features of 28 confirmed cases, 7 suspected cases, and cases related to Ningbo Tian-tong Temple or not were shown in Table 3.
      Table 3Initial chest CT imaging features of 28 confirmed cases and 7 suspected cases with COVID-19 in Ningbo, China.
      ParametersConfirmed cases

      (n = 28)
      Suspected cases

      (n = 7)
      Related to Ningbo Tian-tong Temple

      (n = 21)
      Not related to Ningbo Tian-tong Temple

      (n = 14)
      Chest CT features
       Ground-glass opacity25 (89.3%)7 (100%)21 (100%)11 (78.6%)
       Consolidation10 (35.7%)3 (42.9%)7 (33.3%)6 (42.9%)
       Interlobular septal thickening9 (32.1%)2 (28.6%)8 (38.1%)3 (21.4%)
       Crazy paving pattern10 (35.7%)4 (57.1%)11 (52.4%)3 (21.4%)
       Subpleural line8 (28.6%)1 (14.3%)5 (23.8%)4 (28.6%)
       Bronchial wall thickening13 (46.4%)3 (42.9%)11 (52.4%)5 (35.7%)
      Lung lobes involved
       The left upper lobe19 (67.9%)3 (42.9%)14 (66.7%)8 (57.1%)
       The left lower lobe16 (57.1%)3 (42.9%)10 (47.6%)9 (63.3%)
       The right upper lobe13 (46.4%)2 (28.6%)10 (47.6%)5 (35.7%)
       The right middle lobe11 (39.3%)2 (28.6%)10 (47.6%)3 (21.4%)
       The right lower lobe23 (82.1%)3 (42.9%)15 (71.45)11 (78.6%)
      Lesion distribution area
       Subpleural distribution19 (67.9%)5 (71.4%)13 (61.9%)11 (78.6%)
       Peripheral distribution22 (78.6%)7 (100%)17 (81.0%)12 (85.7%)
       Peri-bronchial distribution2 (7.1%)1 (14.3%)3 (14.3%)0 (0%)
       Diffuse distribution2 (7.1%)0 (0%)2 (9.5%)0 (0%)
      Of the 28 confirmed cases, the most common CT features were bilateral and peripheral GGOs, which were observed in 25 cases (Fig. 1), followed by GGOs with mixed consolidations (10/28). One patient just had micronodular foci at the subpleural basal segment of the lower lobe of the right lung. Two patients were negative on initial CT scans. Of the 7 suspected cases, peripheral GGOs were observed in all of them (Table 3), and these features were similar to the confirmed cases (Fig. 2). Of the 21 cases related to Ningbo Tian-tong Temple rituals, 17 were confirmed to have COVID-19 pneumonia and the remaining 4 were suspected, all of them had GGOs in the lungs during the initial CT scans, which were similar to the confirmed cases from other areas (Fig. 3).
      Fig. 1
      Fig. 1A 66-year-old man with a history of exposure to a patient with COVID-19 pneumonia who came from Wuhan. Initial chest CT scan was performed on day 5 after onset of illness. Axial CT scan (Day 5) showed multi-focal ground-glass opacifications with a crazy-paving pattern in the upper lobes of both lungs, the middle and lower lobes of the right lung, mainly distributed in subpleural or peripheral areas. During follow-up CT scans on days 11, 15, 19 and 23, which showed the size and density of the lesions on both lungs were gradually and significantly decreased.
      Fig. 2
      Fig. 2Case 1 is a 67-year-old woman and case 2 is a 65-year-old woman, both of them had a history of attending Ningbo Tian-tong Temple assembly. The initial chest CT scan was performed on day 8 for case 1 and on day 7 for case 2 after onset illness. Similar chest CT findings were observed that a patchy ground glass opacification was seen in the subpleural area of the right lower lobe of the lung. During follow-up CT scan on day 15, which showed the lesions on both cases were obviously resolved and the size was decreased.
      Fig. 3
      Fig. 3Cases 3 and 4 are both 57-year-old females. Case 3 had a history of exposure to an infected patient outside Ningbo Tian-tong Temple, and the initial CT scan was performed on day 1. Case 4 had a history of attending Ningbo Tian-tong Temple assembly, and the initial CT scan was performed on day 4. Multi-focal GGOs and consolidations were observed on both initial CT scans. During follow-up CT scans on day 7 and 14 for case 3 and day 10 and 20 for case 4, which showed that both lung lesions were significantly resolved.
      In our 35 cases, there were no signs of pericardial effusion, pleural effusion and enlarged lymph nodes on initial CT scans. Three old patients exhibited a progress on the second CT scan, but the lesions were resolved significantly during follow-up CT scans (Fig. 4).
      Fig. 4
      Fig. 4An 86-year-old woman with a history of close contact with a confirmed patient with COVID-19 pneumonia who attended Ningbo Tian-tong Temple assembly. The initial CT scan was performed on day 1 after admission, which showed a patchy ground glass opacification in the subpleural area of the right upper lobe of the lung. Follow-up CT scan on day 7 showed the size of the lesion was enlarged and a new GGO was observed in the subpleural area of the left upper lobe of the lung, which meant the disease had progressed. On day 27, chest CT scan showed the density of the lesions was significantly decreased, which meant the disease was marked remission.

      4. Discussion

      By March 4, 2020, a total of >80,000 confirmed cases with SARS-Cov-2 infection were reported in China []. The clinical characteristics and epidemiological history of COVID-19 have been illustrated by many studies [
      • Huang C.
      • Wang Y.
      • Li X.
      • et al.
      Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China.
      ,
      • Xu X.W.
      • Wu X.X.
      • Jiang X.G.
      • et al.
      Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2) outside of Wuhan, China: retrospective case series.
      ,
      • Chen N.
      • Zhou M.
      • Dong X.
      • et al.
      Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study.
      ,
      • Guan W.J.
      • Ni Z.Y.
      • Hu Y.
      • et al.
      Clinical characteristics of coronavirus disease 2019 in China.
      ]. However, the disease of COVID-19 caused varying degrees of illness and the clinical characteristics were different in different regions [
      • Xu X.W.
      • Wu X.X.
      • Jiang X.G.
      • et al.
      Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2) outside of Wuhan, China: retrospective case series.
      ,
      • Guan W.J.
      • Ni Z.Y.
      • Hu Y.
      • et al.
      Clinical characteristics of coronavirus disease 2019 in China.
      ]. Xu et al. [
      • Xu X.W.
      • Wu X.X.
      • Jiang X.G.
      • et al.
      Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2) outside of Wuhan, China: retrospective case series.
      ]. reported that as of early February 2020, the symptoms of patients with COVID-19 in Zhejiang province were relatively mild compared to patients in Wuhan. However, only limited studies have been reported the chest CT findings of COVID-19 pneumonia and its relationship to clinical features [
      • Wu J.
      • Wu X.
      • Zeng W.
      • et al.
      Chest CT findings in patients with corona virus disease 2019 and its relationship with clinical features.
      ,
      • Xu X.
      • Yu C.
      • Qu J.
      • et al.
      Imaging and clinical features of patients with 2019 novel coronavirus SARS-CoV-2.
      ]. Therefore, in the present study, we investigated the CT imaging features and clinical outcome in a series of patients with COVID-19 in Ningbo, China. Our results showed that the most common CT features are multiple bilateral and peripheral GGOs mixed with mixed consolidations or not in the lungs of patients with COVID-19. Chest CT plays an important role in the diagnosis and monitoring treatment response of this disease. In our sample of 35 patients, there was no reported death.
      Whether there is a gender difference in SARS-Cov-2 infected patients still needs systematic evaluation. Studies vary by region. Xu et al. [
      • Xu X.W.
      • Wu X.X.
      • Jiang X.G.
      • et al.
      Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2) outside of Wuhan, China: retrospective case series.
      ]. reported that most of the COVID-19 patients were male in Zhejiang province. However, no significant difference of sex ratio was revealed in SARS-Cov-2 infection in Beijing [
      • Tian S.
      • Hu N.
      • Lou J.
      • et al.
      Characteristics of COVID-19 infection in Beijing.
      ]. In our results, the female to male ratio is 2.5. As investigating the epidemiological history, we found that almost two thirds of the patients were related to the assembly of Ningbo Tian-tong Temple. This would be explained by the cluster characteristics of COVID-19 pneumonia as specific populations are distributed in certain areas. Moreover, we compared the chest CT imaging features between the infected patients that related to Ningbo Tian-tong Temple and those from other areas. Our results showed that the imaging features were similar to each other and both had bilateral and peripheral GGOs in the lungs. Although some of the patients were older, even 96 years old, the lung lesions were resolved with varying degrees after treatment. In our study, only three patients (8.6%, 3/35) exhibited a progress on the second CT scan which was different from the cases reported by Pan et al. in Wuhan (85.7%, 54/63) [
      • Pan Y.
      • Guan H.
      • Zhou S.
      • et al.
      Initial CT findings and temporal changes in patients with the novel coronavirus pneumonia (2019-nCoV): a study of 63 patients in Wuhan, China.
      ]. This might due to no severe comorbidities were happened in our samples. No “white lung” was seen and nobody died during the course of our study.
      The sensitivity and efficacy of chest CT and RT-PCR in the diagnosis of COVID-19 were compared by several studies [
      • Ai T.
      • Yang Z.
      • Hou H.
      • et al.
      Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases.
      ,
      • Fang Y.
      • Zhang H.
      • Xie J.
      • et al.
      Sensitivity of chest CT for COVID-19: comparison to RT-PCR.
      ,
      • Xie X.
      • Zhong Z.
      • Zhao W.
      • et al.
      Chest CT for typical 2019-nCoV pneumonia: relationship to negative RT-PCR testing.
      ]. Fang et al. [
      • Fang Y.
      • Zhang H.
      • Xie J.
      • et al.
      Sensitivity of chest CT for COVID-19: comparison to RT-PCR.
      ] reported a series of 51 patients and compared the sensitivity of chest CT and RT-PCR in the detection of COVID-19 infection, and the former was much higher than the latter (98% vs. 71%). A large sample of case studies compared the efficacy of CT and RT-PCR in diagnosing COVID-19, which also revealed that chest CT scan had a higher sensitivity than RT-PCR [
      • Ai T.
      • Yang Z.
      • Hou H.
      • et al.
      Correlation of chest CT and RT-PCR testing in coronavirus disease 2019 (COVID-19) in China: a report of 1014 cases.
      ]. Xie et al. [
      • Xie X.
      • Zhong Z.
      • Zhao W.
      • et al.
      Chest CT for typical 2019-nCoV pneumonia: relationship to negative RT-PCR testing.
      ] suggested that repeated swab tests should be recommended for highly clinical suspected cases with negative RT-PCR. However, Chinese and US radiologists show both a high variability in sensitivity (72% to 94%) and in specificity (24% to 100%) for the diagnosis of COVID-19 infection using chest CT [
      • Bai H.X.
      • Hsieh B.
      • Xiong Z.
      • et al.
      Performance of radiologists in differentiating COVID-19 from viral pneumonia on chest CT.
      ]. In our results, 3 of the 28 confirmed cases showed no significant abnormalities on the initial CT scan, possibly because these patients were in the very early stage of COVID-19 pneumonia. Typical CT features of bilateral and peripheral GGOs were observed in the 7 suspected cases (negative RT-PCR). Besides, these 7 cases had clinical symptoms of fever or cough, and a history of close contact with confirmed cases. Influenza A and B infection were excluded from these patients. No evidence showed bacterial superimposed infections. Moreover, the clinical symptoms of fever and cough were relieved and the lung lesions were resolved significantly after the same treatment regimen with the confirmed cases. Therefore, chest CT plays an important role in the diagnosis of COVID-19 but not the golden criteria, a comprehensive diagnosis is very important when patients with negative RT-PCR.
      To our knowledge, this is the first case study to evaluate the chest CT imaging features and clinical outcome of COVID-19 in Ningbo, China. We have all the information about the patients from admission to discharge, including the epidemiological history, clinical features, laboratory analysis and temporal changes of chest CT images. Therefore, to some extent, it can reflect the characteristics of patients with COVID-19 in Ningbo. However, there are some limitations in our study. First of all, the number of the patients enrolled in this study was relatively small owing to a single-center case review. Second, the time from onset illness to the initial chest CT scan was inconsistent, and the time interval of each follow-up CT scans was different, so the temporal changes of CT imaging features to different patients could not be accurately evaluated.
      In conclusion, our results showed that the most common CT features are multiple bilateral and peripheral GGOs with mixed consolidations or not in the lungs for patients with COVID-19. Chest CT plays an important role in the early diagnosis and evaluating treatment response of this disease. The diagnosis of COVID-19 should integrate the epidemiology history, clinical symptoms, laboratory test and CT features when RT-PCR test was negative. There was no reported death in this series of cases. Due to small sample size, multicenter research with a large sample size is warranted.

      Funding information

      None.

      Declaration of competing interest

      There are no conflicts of interest.

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