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Correlation Between Computed Tomography Severity Score and Mortality in Patients with COVID-19 Chest Infection

Introduction: Computed Tomography (CT) is one of the most essential diagnostic tools for early identification and treatment of COVID -19 pneumonia. The objective of this study was to identify the relationship between CT severity score and mortality in COVID-19 patients. Method: A total of 62 patients with confirmed COVID-19 were included in this study. All these patients underwent High resolution computed tomography (HRCT) chest using a standard protocol. The CT severity score in all of these patients was calculated and the results were analyzed by SPSS version 21. Results: A higher CT severity score was associated with higher chances of mortality in the patients of COVID-19. There was no significant association of mortality with the age, sex, and number of lobes involvement Conclusion: HRCT chest can help in the early identification of the patients who need to be admitted to the Intensive care unit. Early admission and intervention to patients with high CT severity scores can help to reduce mortality.


INTRODUCTION
In late December 2019, an outbreak of new coronavirus disease (COVID-19) caused by Severe acute respiratory syndrome coronavirus 2 ( SARS-CoV-2) was reported in Wuhan city, China. 1 The disease rapidly crossed the international borders spreading all around the globe. On March 11, 2020, the World Health Organization (WHO) declared the novel coronavirus outbreak to be a pandemic. 2 In Nepal, the first case of COVID-19 was reported on 23rd January 2020. 3 The first wave was subsequently followed by second and third waves in various parts of the world. In Nepal currently, we are entering the third wave. Several studies have reported the Computed Tomography (CT) findings of COVID-19 Pneumonia. [4][5][6] However, the outcome of patients has not been definite in many of these series. Therefore, the estimation of risk factors for severe disease and death in these earlier studies is not very strong, and there are limited data available about the prognostic application of CT chest. This study aimed to describe the relationship between chest CT severity score and COVID-19 mortality.

METHODS
It was a cross-sectional observational study conducted in the Department of Radiology of Manipal teaching hospital, Pokhara. The study was conducted over one and half months from 17 th May 2021 to 5 th July 2021. Informed consent was taken from the patients prior to their enrollment into the study. Ethical clearance was obtained before the study from the institutional review board of Manipal Teaching Hospital. All the Reverse transcription-polymerase chain reaction (RT-PCR) positive COVID-19 patients with chest symptoms of age ≥18 years sent to the radiology department for Highresolution CT (HRCT) Chest were included in the study. All patients underwent CT chest in Manipal teaching hospital using 128 slice CT (PHILIPS). CT scan was done using standard protocol to minimize radiation dose to the patient. Axial sections with 3 mm slice thickness and FOV of 400 mm were obtained. Tube current of 20-30 mA, tube voltage of 120-140 kV, matrix of 512, pitch 1.078, and rotation time of 0.75 s were used.
Sagittal and coronal reformatted images were subsequently obtained. No contrast material was used. Standard safety precautions as implemented by WHO were followed. All CT scan images were analyzed and reviewed by a radiologist. The severity score was calculated based on lung involvement percentage for each patient by scoring the percentage of each lobe involvement individually and was given a score from 1 to 5 were; Score 1 represented < 5% involvement Score 2: 5-25% involvement Score 3:26-50% involvement Score 4: 51-75% involvement Score 5: > 75% involvement. Then, the final score was the sum of individual lobar scores and was out of 25 (total score); the total lung involvement was then obtained by multiplying the total score by four. 7 Data regarding age, sex, mean CT severity score, mean percentage of lung involvement, and the number of lobes involved were recorded in the performed performa. The collected data were tabulated and entered in an MS excel sheet. Analysis was done by using SPSS 21.0. A logistic regression test was performed to ascertain the effects of age, sex, CT score, Percentage of lung involvement, and several lobes involved on the likelihood of mortality of COVID-19 patients. Statistically significant results were considered at a p value of < 0.05.

RESULTS
A total of 62 patients with laboratoryconfirmed COVID-19 infection were included in our study. Overall, the mean age was 57.2 ± 15.9 years with an age range of 20 to 90 years. A clear male preponderance (61.3%) was noted with a male: female ratio of 1 were males and 7(29.2%) were females. The Mean age of the patient who survived was 54.2±13.3 years compared to the mean age group of patients who died which was 62.0±18.5 years (Table 2).  Table  4). Most of the patients who died had severe disease with a CT severity score of more than 17. Among the patients who recovered, 63.2% had moderate disease with CT severity score of 8 to 17 (Table 5).

DISCUSSION
With the spread of the Novel coronavirus, it has been a growing concern for scientists all around the world. The pathogenesis of COVID-19 is still a mystery. However, diffuse alveolar damage and progressive respiratory failure is the major cause of death in these patients. 8 The predominant finding in HRCT of COVID-19 Patients includes multiple ground-glass opacities and/or consolidations. 9 In this study, we have analyzed the high-  10 Furthermore, in the study done by Homayounieh F et al, they too found that higher CT severity score in COVID-19 patients was associated with increased mortality as in our study. 11 Similarly, in a study done in China by Yuan M et al in 2019, they found that the median CT score of the mortality group was higher compared to the survival group. 12 Feng Z et al found CT severity score as an independent factor for progression in COVID-19 pneumonia patients as in our study. 13 In severe illness, there is direct damage to the lungs by the virus, causing inflammatory changes in the alveolar walls, limiting oxygen exchange, leading to acute respiratory distress, pulmonary fibrosis, and ultimately death. In addition, autopsy of patients who died of COVID 19 disease also detected a significant pulmonary thromboembolizing effect. [14][15][16] The results of our study show that mortality was significantly higher in patients with higher CT severity scores. Thus, patients with higher CT severity scores could benefit from early intensive care and treatment.
HRCT chest can be of prognostic significance in COVID-19 patients and help as an adjunct tool to patient prognostication.

CONCLUSION
In patients of COVID-19, a higher CT severity score was associated with increased chances of mortality. Hence, HRCT chest can be of prognostic use in COVID-19 patients and help in early admission of COVID-19 patients preventing mortality.