The role of computed tomography chest in correlating with the severity and outcome of COVID-19 patients admitted in a tertiary care hospital in South India

A Kirubanandam; Gayathri Anur Ramakrishnan; Sunder Kapali

doi:10.4103/japt.japt_4_23

ORIGINAL ARTICLE

Year : 2023 | Volume : 6 | Issue : 1 | Page : 7-13

The role of computed tomography chest in correlating with the severity and outcome of COVID-19 patients admitted in a tertiary care hospital in South India

A Kirubanandam¹, Gayathri Anur Ramakrishnan², Sunder Kapali²
¹ Department of Respiratory Medicine, Apollo Hospital, Chennai, Tamil Nadu, India
² Department of Radiodiagnosis, Apollo Hospital, Chennai, Tamil Nadu, India

Date of Submission	07-Feb-2023
Date of Decision	09-Mar-2023
Date of Acceptance	14-Mar-2023
Date of Web Publication	29-Apr-2023

Correspondence Address:
Dr. A Kirubanandam
No. 366, Eswaran Koil Street, Sevoor PO, Arni, Tiruvannamalai - 632 316, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/japt.japt_4_23

Abstract

Aim: To assess the role of computed tomography (CT) chest in correlating with the severity and outcome of COVID-19 Patients. Background and Materials and Methods: A prospective study was done on 160 hospitalized patients who were COVID-19 positive by reverse transcription-polymerase chain reaction in Apollo Hospital, Greams Road, Chennai, India. We collected epidemiological data, comorbidities, clinical manifestations, oxygen requirement, and CT chest details of all patients. All images were reviewed by a single consultant radiologist and CT chest severity scoring was done as per the guidelines published in the American Journal of Radiology. CT chest severity score (CTSS) was then compared with clinical severity and various parameters. Results: This study included 160 hospitalized COVID-19 patients with a mean age of 61 ± 13.97 years. Male (74.4%) patients were more when compared to female patients (25.6%). Majority of the patients were belong to mild category (44.38%), followed by severe (28.7%) and moderate (26.8%) categories. Fever (73.8%) was the most common symptom. Diabetes mellitus (57.5%) was the most common comorbidity of COVID-19 patients in our study, followed by hypertension (55%). The average CTSS of mild category was 7.4 ± 4.7; for moderate category, the mean CTSS was 14.6 ± 5.78; and for severe category, it was 18.3 ± 5.28. There was increasing trend of severity score, as clinical severity increases which was statistically significant (P = 0.0001). The mean CTSS of patients who required no oxygen, low flow oxygen, high flow oxygen, noninvasive ventilation, and intubated patients was 8.3 ± 5.71, 14.84 ± 5.39, 18.17 ± 5.7, 18.17 ± 6.04, and 22.18 ± 4.07, respectively, which was statistically significant (P = 0.0001). The mean CTSS of patients discharged without oxygen requirement was 11.09 ± 6.48 and patients discharged with oxygen requirement was 18.09 ± 6.12 (P = 0.001). The mean CTSS of patients who died was 20.27 ± 4.62. Conclusion: There was a significant correlation between CT chest severity score and clinical severity and oxygen requirement. CT chest is one of the best screening tools for rapid identification as well as to predict the clinical severity; thereby, it helps the clinician in managing the COVID-19 patients at crucial points during the progression of disease.

Keywords: COVID-19, computed tomography chest severity score, oxygen requirement

How to cite this article:
Kirubanandam A, Ramakrishnan GA, Kapali S. The role of computed tomography chest in correlating with the severity and outcome of COVID-19 patients admitted in a tertiary care hospital in South India. J Assoc Pulmonologist Tamilnadu 2023;6:7-13

How to cite this URL:
Kirubanandam A, Ramakrishnan GA, Kapali S. The role of computed tomography chest in correlating with the severity and outcome of COVID-19 patients admitted in a tertiary care hospital in South India. J Assoc Pulmonologist Tamilnadu [serial online] 2023 [cited 2023 May 29];6:7-13. Available from: https://www.japt.in//text.asp?2023/6/1/7/375460

Introduction

COVID-19 or SARS-CoV-2 is a form of betacoronaviruses associated with human severe acute respiratory syndrome and Middle East respiratory syndrome coronavirus. It is a new respiratory tract infecting agent which emerged in Wuhan City of China, in December 2019.^[1] It has spread rapidly all over the world, and as per the WHO report May 2021, there have been 169 million confirmed cases.^[2] The mortality is substantially high among critically ill COVID-19 patients. Hence, early detection, rapid isolation, and disinfection are the most efficient ways to control the pandemic.

In this current scenario, clinicoradiological diagnosis of COVID-19 has become very crucial. Thin-section chest computed tomography (CT) is more sensitive (97%) than chest X-ray, in picking up abnormal changes in the lung parenchyma, in early stages of the disease.^[3] It acts as a valuable screening tool. Typical CT chest findings in COVID-19 patients are bilateral peripheral and basal predominant ground-glass opacities (GGOs) with or without consolidation and bronchovascular thickening.^[4] It plays an important role in diagnosis and identification of risk factors for the progression of COVID-19 and it is considered the first-line imaging modality in highly suspected cases.^[5]

The extent and severity of lesions has a major influence on the prognosis. The main purpose of this study is to see the correlation between the CT chest severity score and clinical severity of COVID-19 patients. The utility of the CT chest severity score to assess the prognosis and mortality from COVID-19 has been studied.

Aim and objectives

The study was aimed to assess the role of CT chest in correlating with the severity and outcome of COVID-19 patients. The correlation between CT chest severity and clinical severity in patients admitted with COVID-19 pneumonia and the prognosis and clinical outcome of the patients were also studied.

Materials and Methods

The prospective observational study was done on 160 COVID-19-positive patients admitted in Apollo Main Hospitals, Greams Road, Chennai, India, from January 2021 to August 2021.

Inclusion criteria

Patients admitted with COVID-19 symptoms, who were turned out to be positive by reverse transcription-polymerase chain reaction (RT-PCR) and CT Chest.

Exclusion criteria

Age <18 years of age
Patients with preexisting interstitial lung disease, bronchiectasis, tuberculosis.

Data collection

Patients who were presented with symptoms like fever, cough, and breathlessness were tested and those were confirmed as COVID-19 positive by RT-PCR on nasopharyngeal swab and sampling from lower respiratory tract were included in the study. Epidemiological data and detailed clinical history including comorbidities, symptoms, and signs were collected.

According to clinical management protocol COVID-19, patients were classified as mild, moderate, and severe categories.

Mild – Patients without evidence of breathlessness or hypoxia (SpO₂ <94% at room air)
Moderate – Patients with SpO₂ 90%–94% at room air/Respiratory rate >/min
Severe – Patients with SpO₂ <90% at room air/respiratory rate >30/min/blood pressure <90/60 mmHg/acute respiratory distress syndrome/end organ damage.

CT chest scanning of the patient was done after taking adequate COVID-19 precautions. Data pertaining to clinical progress of the patient and final outcome were collected and correlated with the CT severity score. All CT chest scans were reviewed by a single consultant radiologist to avoid bias.

The CT score was assigned according to GGOs involvement in the lobes with scores defined as follows.

Score 0 – Denotes no lobe involvement
Score 1 – Denotes <5% of lobe involvement
Score 2 – Denotes 5%–24% of lobe involvement
Score 3 – Denotes 25%–49% of lobe involvement
Score 4 – Denotes 50%–75% of lobe involvement
Score 5 – Denotes more than 75% of lobe involvement.

If crazy paving pattern appeared in one lobe, the score is increased by 1, and if consolidation appeared in one lobe, the score is increased by 2.^[6]

Therefore, score of 7 is maximum for a lobe. The total score is defined as the sum of the scores of each of the 5 lobes and it ranges from 0 to 35 with the highest possible score indicating consolidation in all 5 lobes [Figure 1], [Figure 2], [Figure 3].

Figure 1: CT chest of a patient with mild COVID pneumonia (CTSS-6/35). CT = Computed tomography, CTSS = Chest CT severity score

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Figure 2: CT chest of a patient with moderate COVID pneumonia (CTSS-14/35). CT = Computed tomography, CTSS = Chest CT severity score

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Figure 3: CT chest of a patient with severe COVID pneumonia (CTSS-29/35). CT= Computed tomography, CTSS = Chest CT severity score

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Statistical analysis

All continuous variables were tested for the normality using Shapiro–Wilk test. If the variables are normally distributed, they were expressed as mean + standard deviation, otherwise median (interquartile range). Comparison of CT severity score which is of continuous in nature was compared with clinical staging by analysis of variance, if they were normally distributed; otherwise, Kruskal–Walli H-test was used. Comparison of continuous variables like oxygen requirement, intubation, and mortality were done by independent sample t-test, if they were normally distributed, otherwise Mann–Whitney U-test.

Pearson's correlation coefficient was computed to know the association between CT severity score and length of stay and the interval between CT chest and the onset of symptoms. Comparison of categorical variables was done by either Chi-square test. Data analysis was carried out b IBM SPSS Statistics for Windows version 25.0, Armonk, NY:IBM Corp. All P < 0.05 were considered statistically significant.

Results

In our study, after ethical committee approval, 160 hospitalized COVID-19 patients were included from January 2021 to August 2021.

Most of the patients were in the mean age of 61 ± 13.97 years. The mean age of mild category was 58.17 ± 15.83 years. The average age of moderate category was 62.67 ± 11.90 years, whereas for severe category, it was 66.41 ± 11.16 years [Graph 1].

Male (74.4%) patients were more when compared to female patients (25.6%). Around 40.3% of males were classified as mild category, 27.7% as moderate category, and 31.9% as severe category. Among females, 56.1%, 24.4%, and 19.5% were classified as mild, moderate, and severe category, respectively [Graph 2].

Fever (73.8%) was the most common symptom, followed by cough (45%), myalgia (35.6%), dyspnea (28.7%), loose stools (8.8%), sore throat (6.3%), loss of smell (1.9%), and loss of taste (0.6%) [Graph 3].

Majority of the hospitalized patients were classified as mild category, followed by severe and moderate categories. Diabetes mellitus (57.5%) was the most common comorbidity of COVID-19 patients in our study, followed by hypertension (55%), coronary artery disease (20%), hypothyroidism (10%), chronic kidney disease (5%), other lung diseases (3.1%), and chronic liver disease (1.9%) [Graph 4]. Most of the patients had CT chest within 7 days of onset of symptoms (72.5%).

Computed tomography chest severity score versus clinical severity

The mean CT chest severity score of total hospitalized patients was 12.49 ± 7.012. The average CT severity score (CTSS) of mild category was 7.4 ± 4.7; for moderate category, the mean CTSS was 14.6 ± 5.78; and for severe category, it was 18.3 ± 5.28 [Graph 5].

Cyclical threshold value versus clinical severity

The mean CT value of mild category patients was 24.67 ± 4.52; for moderate category, it was 23.7 ± 4.35; and for severe category, it was 25.31 ± 4.64 [Graph 6].

Correlation of computed tomography chest severity score with oxygen requirement

The mean CTSS of patients who required no oxygen was 8.3 ± 5.71. For patients who required low flow oxygen, the mean CTSS was 14.84 ± 5.39, whereas for patients required high-flow oxygen and noninvasive ventilation, the mean was 18.17 ± 5.7 and 18.17 ± 6.04, respectively. The mean CTSS of intubated patients was 22.18 ± 4.07 [Graph 7] and [Table 1].

Table 1: Correlation of computed tomography chest severity score with oxygen requirement

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Correlation of computed tomography chest severity score with outcome

The mean CTSS of patients discharged without oxygen requirement was 11.09 ± 6.48 and patients discharged with oxygen requirement was 18.09 ± 6.12. The mean CTSS of patients who died was 20.27 ± 4.62 [Graph 8] and [Table 2].

Table 2: Correlation of computed tomography chest severity score with outcome

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Correlation of computed tomography chest severity score with length of hospital stay

In this study, CT chest severity score correlated well with the length of hospital stay which was statistically significant with P = 0.0001 [Graph 9] and [Table 3].

Table 3: Correlation of computed tomography chest severity score with length of hospital stay

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Discussion

We included 160 hospitalized COVID-19 patients who were COVID-19 RT-PCR positive and with CT chest done. The main goal of our study was to evaluate the correlation between CT chest severity score and clinical severity. This was the first prospective observational study of this kind done at this tertiary care hospital.

The purpose of our study was to reduce the time in diagnosing COVID-19 patients and to be able to decide on early isolation and triage the patients in emergency room. CT chest abnormalities can occur in a very early stage of COVID-19. This study also highlighted the role of CT severity score in determining the prognosis in COVID-19 patients.

The mean age of the patients was 61 ± 13.97 ranging from 21 to 94 years. The mean age of mild category was lower than that of moderate and severe category, which showed that increasing age is a risk factor for clinical severity.^[7] Older patients have relatively higher incidence of comorbidities, when compared to younger patients.^[8] Older age is also considered an independent risk for mortality.^[7]

Out of 160 patients included in our study, 74.4% were male and 25.6% were female. There is a strong and clear association between male gender and SARS-CoV2 susceptibility.^[8] In our study, 46 patients were classified as severe category, out of which 38 patients (82.6%) were male and 8 patients (17.4%) were female. It clearly showed that there was an increased risk of severity among males when compared to females. Similar observations are seen in a study conducted by Vahidy et al. In this study, there is increased admission and in-hospital mortality in male patients.^[9] The high risk behavior including alcohol use, smoking, and presence of more comorbidities could be one of the reasons for gender disparities in mortality and severity of COVID-19 patients.^[10] Men respond differently to foreign as well as self-antigens and sex differences in immune response are well documented.^[11] The presence of angiotensin-converting enzyme 2 receptors and the cellular serine protease TMPRSS2, which are responsible for viral entry and priming, may vary between males and females. The TMPRSS2 is expressed in airway epithelium but predominantly expressed in prostate epithelium.^[12],[13]

The most common presenting symptom in our study was fever which was seen in 73.8% of the patients. Other common symptoms were cough (45%), myalgia (35.6%), dyspnea (28.7%), loose stools (8.8%), sore throat (6.3%), loss of smell (1.9%), and taste (0.6%). These findings had also been observed in a study by Larsen et al.,^[14] wherein the most common symptom is fever followed by respiratory symptoms and gastrointestinal symptoms.

Sanyaolu et al. observed that there is an increased chance of COVID-19 infection in patients with comorbidities.^[15] The most common comorbidity associated with COVID-19 patients in this study was diabetes mellitus (57.5%), followed by hypertension (55%) and CAD (20%). Diabetic patients are more likely to have increased severity of COVID-19. Increased mortality rate is seen in patients with poor blood glucose control than those with better glucose control.^[16] Elevated glucose in monocytes directly increases the replication of SARS-CoV2. Glycolysis causes activation of hypoxia inducible factor 1 alpha and production of mitochondrial reactive oxygen species, which leads to sustained replication of SARS-CoV2.^[17]

Correlation of computed tomography chest severity score with clinical severity

In our study, the mean CT severity score was comparatively higher in severe category than moderate and mild categories. It was progressively increasing, as the clinical severity increased. The CT severity score correlated well with clinical severity and it was statistically significant. Similar observations were seen in a study of 902 patients by Saeed et al. They found that the 25-point CT severity score correlated with the COVID-19 clinical severity.^[17] The study done by Ribeiro et al. included 658 hospitalized patients and it was found that RAD-COVID score was correlated positively with clinical severity.^[18]

Correlation of computed tomography severity with oxygen requirement

CT severity score correlated well with the oxygen requirements in our study and it was found to be statistically significant. The delivery of oxygen depends on patient's demand, source of oxygen, and delivery device. Hence, it is very essential, while choosing the appropriate mode of oxygen delivery.

Patients with COVID-19 pneumonia experience “happy hypoxia”. Patients may not have symptoms like breathlessness even though they have hypoxia. There is a huge mismatch between clinical assessment and pulse oximetry. The researchers at Loyola University did a study, collecting details from 58 hospitals, to record incidence of hypoxia in patients. They concluded that around 16 patients had hypoxia without any symptoms.^[19],[20]

In our study, we found that patients who were intubated had higher mean severity score than those required low-flow oxygen. This indicates that with increase in CT chest severity score, the oxygen demand proportionally increased as well. Higher CT severity score corresponds to poorly aerated lung areas and hence the severe disease. Higher CT severity score also serves a predictor of pulmonary dysfunction which is measured by PaO₂/FiO₂ ratio, degree of oxygen support, invasive ventilation, and is a risk factor for in hospital mortality.^[21] CT severity score was useful in predicting the oxygen requirement in COVID patients. Aalinezhad et al. had similar findings in their study of 270 COVID-19 patients and concluded that there was an inverse relationship between SpO₂ and CT severity score.^[21]

Correlation of computed tomography chest severity score with outcome

The mean CT chest severity score of patients discharged without oxygen requirement was 11.09 ± 6.4. Patients discharged with oxygen support had mean CT chest severity score of 18.29 ± 6.12. The mean CT severity score of patients who died was 20.27 ± 4.68. This shows that patients with higher CT severity score may benefit from early Intensive care unit (ICU) admission and can help inpatient discharge in emergency room, especially in settings with limited ICU beds and resources.^[22],[23]

Death rate was significantly increased in patients with higher CT severity score which was noted in many other studies.^{[18],[24],[25],[26]} Francone et al. enrolled 130 COVID-19 patients in a single-center study. They found that risk of death was significantly higher in patients with CT severity score of more than or equal to 18.^[24] Tabatabaei et al. retrospectively studied 30 laboratories confirmed COVID-19 patients without comorbidities and found that CT severity score is the only statistically significant CT predictor of mortality. They concluded that a score of 7.5 as cutoff point of CT severity score with highest sensitivity (0.83) and specificity (0.87).^[25]

Correlation of computed tomography chest severity score with length of hospital stay

In our study, CT chest severity score had a positive correlation with length of hospital stay with correlation coefficient of 0.404. As the CT severity score increases, the hospital stay is also increased which is statistically significant with P = 0.0001. A systemic review done by Rees et al.^[27] has suggested that length of hospital stay varies depending on multiple factors such as different timing within pandemic, availability of bed and its demand, variations in admission, and discharge criteria.

Limitations

In this study, we have not included COVID-19 RT-PCR-confirmed patients who were treated as outpatient. It is a single-center observational study. The interval between CT chest and onset of symptoms is crucial. We did not analyze the cutoff date to take CT chest in this study.

Conclusion

CT chest plays an important role as a screening tool in suspected COVID-19 patients. It is useful in risk stratification of COVID-19 patients in emergency room and to triage the patients. The assessment of CT severity score is useful for clinicians for the purpose of early diagnosis and prompt treatment. This study clearly showed that the CT severity scoring correlated well with clinical staging of patients. CT chest severity score can be helpful in predicting the short-term outcome of patients. We also found that the CT chest severity correlated well with length of in hospital stay. We can conclude from our study that the CT chest severity score is an important tool in predicting the severity, short-term outcome, and prognosis of COVID-19 patients.

Recommendations

To validate our findings in the study, we require large scale, multicenter long-term randomized control trials.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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