Chest computed tomography severity score is a reliable predictor of mortality in patients with chronic obstructive pulmonary disease co-infected with COVID-19

In December 2019, a novel beta-coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in Wuhan city, China. The infectious disease caused by this novel coronavirus was named “coronavirus disease 2019 (COVID-19)” by WHO in February 2020. One month later in March 2020, WHO officially declared the disease a globally pandemic and COVID-19 has been a global health crisis for more than two years [1]. The clinical spectrum of SARS-CoV-2 infection ranges from asymptomatic patients to critically ill ones with acute respiratory distress syndrome and multiorgan dysfunction [2]. Male individuals, elderly people, and patients with comorbidities such as diabetes, hypertension, obesity, and cardiovascular disease are at higher risk of poor COVID-19 outcomes and require more attention [3‐7].

Early in the SARS-CoV-2 pandemic there was a growing concern about the outcomes in chronic obstructive pulmonary disease (COPD) patients who developed COVID-19. COPD, a common cause of disability and death worldwide, is a persistent dysfunction of the lung characterized by airflow limitation due to inflammation of the airway and/or alveolar abnormalities. COVID-19 patients with preexisting COPD are among high-risk groups due to various complications. These complications include virus-induced exacerbations, impaired lung function, compromised immune responses, and upregulation of angiotensin-converting enzyme 2 (ACE-2) receptor. ACE-2 receptor facilitates SARS-CoV-2 entry into cells putting these patients at higher risk of COVID-19 infection [8‐13].

Chest computed tomography (CT) is an effective modality for COVID-19 diagnosis and monitoring the progression of the disease. Studies have discussed that CT imaging has a sensitivity higher than RT-PCR (98% compared to 71%); therefore, chest CT can be used as a screening tool in suspected cases of COVID-19. According to previous studies, ground glass opacities and consolidations with peripheral and subpleural distribution are two main CT findings in COVID-19 [14‐19]. The extent and nature of these findings are predictive of prognosis [15]. There are several studies that use a chest CT-based scoring system to determine the risk of disease deterioration and poor outcomes in patients with COVID-19. These studies have demonstrated that higher scores in patients’ CT are associated with higher mortality and severe forms of COVID-19 [18, 20‐24]. However, there are limited data on predictive value of a CT severity score in COVID-19 patients who have preexisting COPD. Taking that into consideration, the aim of the current study was to investigate the severity of the disease of COVID-19 in patients with COPD history based on CT severity score and to evaluate its predictive power in the mortality of patients.

This was a single-center retrospective study conducted on COPD patients diagnosed with COVID-19 who were hospitalized in Ardabil Imam Khomeini hospital, northwestern Iran from March 2020 to February 2022. All patients who underwent chest CT scan within 24 h of admission in the radiology department of the hospital, included in this study. The diagnosis of COVID-19 was confirmed with a positive RT-PCR for SARS-CoV-2 based on nasopharyngeal and oropharyngeal swabs. Exclusion was determined by certain conditions: (a) patients with a negative RT-PCR, (b) absence of CT findings in mild patients, (c) inadequate quality of chest CT images for analysis, and (d) age below 18 years. This study was approved by the ethics committee (IR.ARUMS.REC.1400.312).

The most important findings of the current study were as follows: 1- The mean CT severity score in patients who died was detectably higher than those who recovered. 2- Based on the ROC and Kaplan–Meier survival curves, it was revealed that CT severity score was a valuable criteria in the diagnosis of mortality in COPD patients with COVID-19. 3- Results from multivariate Cox regression model indicated that lower lung lobes severity score were significantly associated with survival.

Many studies have been conducted to identify the role of a quantitative CT scoring system in predicting disease severity in COVID-19 patients. To the best of our knowledge this is the first study that focuses on COPD patients infected by SARS- CoV-2 to evaluate CT findings based on a quantitative scoring system. A previous study used a quantitative CT emphysema score to examine its association with clinical outcome in COPD and COVID-19 patients, which demonstrated that scores higher than 5% are associated with disease severity. However, this study did not include COVID-19 specific radiologic findings in the scoring system [27]. According to current data COPD is not a frequent comorbidity in COVID-19 patients [22, 28]. In contrast, some studies have demonstrated that COPD patients were more susceptible to the critical form of COVID-19 [29, 30]. This can be due to impaired lung function in COPD patients and higher ACE-2 expression in these patients which may facilitate viral entry.

The results of the current study revealed that the mean CT score was higher in the non-survival patients in comparison to the survival group. Patients with severe and critical disease also had higher CT scores than moderate cases. This was in agreement with previous studies that suggested higher CT scores in COVID-19 patients are associated with higher mortality and increase the risk of developing severe and critical types of the disease [21, 31]. In addition, it was found that GGO, a crazy-paving pattern, and consolidations are the most frequent findings in COPD patients with COVID-19 and the findings are more predominant in peripheral and they are mostly bilateral, which was consistent with recent studies [14, 16, 17, 19].

During the coronavirus pandemic, the use of different indicators to diagnose the disease prognosis in patients with COVID-19 has been of interest. In our previous study, systemic inflammation indices were used to diagnose the severity of the disease in COVID-19 patients [32‐35]. On the other hand, the effectiveness of severity score in patients with COVID-19 has been reported in some studies [18, 36‐39]. The results of the current study showed that CT severity score was a valuable measure in diagnosing the severity of the disease in COPD patients infected with SARS-CoV-2. Although all the levels of the right and left lungs (upper, middle, and lower) based on ROC and Kaplan–Meier curves were useful in diagnosing the mortality of patients, the lower levels of the lungs were very efficient.

To our best knowledge, multivariate Cox regression analysis showed that among the different levels of the right and left lung (upper, middle, and lower), the lower level of the right lung remained with survival. It seems that in COPD patients with COVID-19, the involvement of the lower parts of the lungs is associated with a poor prognosis of the disease, which requires further studies.

The limitations of the study were as follows: 1- This study was conducted retrospectively and in a single center. 2- The sample size for the evaluation of COPD patients with COVID-19 was moderate, and a large number of patients is required for more detailed investigations. 3- Although the CT severity score of patients at admission is used to determine the prognosis of the disease, but each patient may be hospitalized with a different severity of the disease. 4- Different stages of COPD may have influenced the results of the study, which could not be evaluated due to the lack of spirometry findings. 5- Medicines used by patients to treat COPD before hospitalization could not be reported due to lack of registration.

COPD patients are particularly vulnerable to SARS-CoV-2 infection as a result of their specific treatments and accompanying illnesses. Establishing the intensity of the disease at the start of hospitalization in COPD patients can manage their treatment effectively. The current study demonstrated that the CT severity scoring system can be used as a beneficial tool for estimating disease severity and predict prognosis in COVID-19 COPD patients. Interestingly, the lower lobes of lung involvement showed an excellent predictive power for mortality rates in the case of COPD patients infected with COVID-19.