Chest CT findings of COVID-19 pneumonia by duration of symptoms

Chest CT findings of COVID-19 pneumonia by duration of symptoms.

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To evaluate lung abnormalities on thin-section computed tomographic (CT) scans in patients with COVID-19 and correlate findings to duration of symptoms.


Thin-section CT could provide semi-quantitative analysis of pulmonary damage severity. This disease changed rapidly at the early stage, then tended to be stable and lasted for a long time.

Since December 2019, many unexplained pneumonia’s had been reported, initially related to exposure at the Huanan Seafood Market in Wuhan city, Hubei province, China [1]. The pathogen was soon identified as a coronavirus, similar to those involved in severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV). The novel coronavirus was named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by international committee on taxonomy of viruses (ICTV), capable of infecting humans, on 11 February 2020 and the disease was termed COVID-19 by world health organization (WHO) [1]. Based on the current epidemiological surveys, the incubation period of this disease is 1–14 days, mostly 3–7 days. Fever, dry cough and fatigue are the main manifestations. A few patients have symptoms such as nasal obstruction, runny nose, sore throat, myalgia and diarrhea. Seriously ill patients may rapidly progress to ARDS. The outbreak of COVID-19 has been declared a public health emergency of international concern by WHO. As of March 18, 2020, a total of 186,777 confirmed cases with COVID-19 pneumonia have been reported globally, including 7480 deaths (4.0 %). A specific viral nucleic acid assay using real time reverse transcription - polymerase chain reaction (RT-PCR) was quickly developed to confirm the diagnosis of COVID-19 [2,3]. However, from the recently published literature, some patients with likely 2019-nCoV infection might have initial negative RT-PCR results [4]. Reasons for false negative RT-PCR tests may include insufficient cellular material for detection and improper extraction of nucleic acid from clinical materials [5,6]. According to current experience, lung CT imaging may manifest abnormalities earlier than RT-PCR testing. Currently, high-resolution CT has been included as one of the main tools for screening, primary diagnosis, and evaluation of disease severity [7].

The aim of this study, therefore, was to evaluate lung abnormalities on thin-section computed tomographic (CT) scans in patients with COVID-19 and correlate findings to duration of symptoms.

Study population

Institutional review board approval was obtained, and informed consent for this retrospective study was waived. The anonymous data were collected and analyzed to facilitate better clinical decisions and treatment. In total, 112 patients (mean age, 55.8 years; range, 12–89 years), including 51 males (mean age, 58.3 years; range, 25–89 years) and 61 females (mean age, 53.7 years; range, 12–86 years) with confirmed COVID-19 pneumonia, were included in our study between February 2020 and March 2020 (Table 1). All patients underwent a series of chest CT scans to evaluate the severity of the disease and observe the change of the disease until the acute exudative lesions were obviously absorbed or disappeared.

Diagnostic and cure criteria of COVID-19 pneumonia

Based on the preliminary diagnosis and treatment protocols from the National Health Commission of the People’s Republic of China, the diagnostic criteria of COVID-19 pneumonia were as follows : 1. Epidemiological history: travel or residential history of Wuhan city and surrounding areas, or other communities with case reports within 14 days before the onset of the disease; exposure history to infected persons with 2019-nCoV (positive for nucleic acid detection) within 14 days before onset; 2. Clinical manifestations and laboratory indicators: fever and / or respiratory symptoms, imaging characteristics of pneumonia, and / or normal or decreased white blood cells count or decreased lymphocyte count; and 3. Confirmed diagnosis: real-time RT-PCR detection of COVID-19 in throat swabs or lower respiratory tract; highly homologous with other novel coronavirus through virus gene sequencing [7,8]. The patients with confirmed COVID-19 pneumonia were all hospitalized and isolated for treatment. The discharge criteria were: 1. Afebrile for more than 3 days; 2. Respiratory symptoms significantly improved; 3. Obvious improvement of acute exudative lesions on chest CT; and 4. Two consecutive negative COVID-19 nucleic acid tests at least 24 h apart.

CT protocol

CT scans were performed at the end-inspiration level with patients in supine position and arms raised. Two CT systems were used with the following parameters: GE Discovery CT750 HD, 1.25 mm section thickness for reconstruction, 1.25 mm gap, tube voltage 120 kV with automatic tube current modulation, DFOV 40.0 × 46.6 cm; Siemens Somatom Definition, Siemens Healthineers, Germany, 1.0 mm section thickness for reconstruction, 1.0 mm gap, tube voltage 120 kV with automatic tube current modulation, DFOV 36.8 × 42.9 cm.

Chest CT image analysis

Two experienced radiologists with 13 and 11 years of clinical experience in chest CT radiology respectively reviewed the thin-section CT images respectively and reached a decision in consensus. The observers categorized the predominant patterns on CT scans as ground-glass opacification (GGO, hazy areas of increased attenuation without obscuration of the underlying vessels), crazy-paving pattern (GGO with interlobular and intralobular septal thickening), consolidation (homogeneous opacification of the parenchyma with obscuration of the underlying vessels), and linear opacities (disordered arrangement of coarse linear or curvilinear opacities or fine subpleural reticulation). On the scans, some other minor signs such as air bronchogram, cavitation, bronchiectasia, pleural effusion, pericardial effusion, pneumothorax and mediastinal lymphadenopathy (defined as a lymph node greater than 1 cm in short-axis diameter) were also noted. The distribution of pulmonary lesions was noted as peripheral (predominantly subpleural, involving mainly the peripheral one-third of the lung), central (predominantly lung hilum, involving mainly the central two-third of the lung), and diffuse (both subpleural and central regions). The involvement of pulmonary lesions was also noted as single lobe, unilateral multilobe and bilateral multilobe.

Statistical analysis

Statistical analyses were performed using SPSS version 23.0 (SPSS, Inc., Chicago, IL) and Graphpad prism version 7.0 (GraphPad software Inc., USA). Quantitative data were presented as mean ± standard deviation (SD) (minimum - maximum). The counting data were presented as count (percentage of total). Quantitative data were tested first with the Kolmogorov - Smirnov test for normality and Levene test for homogeneity of variance. The comparisons of paired and non-paired quantitative data were evaluated using Wilcoxon test and Mann-Whitney U test between two groups, and Friedman test and Kruskal-Wallis test among multiple groups. Differences were considered significant at P < .05.