This study indicated that patients who were hospitalized with COVID-19 tended to be older than those in the general population. Among all patients, 68% had one or more coexisting medical conditions, such as hypertension, cardiac disease, or chronic obstructive pulmonary disease. Our finding that COVID-19 is more common in older adults with coexisting chronic diseases is consistent with previous publications [11, 15, 16]. Indeed, elderly men with underlying diseases appear to have the highest risk for development of COVID-19 [17]. The most common symptoms at the onset of illness were fever, dry cough, myalgia, fatigue, dyspnea, and anorexia. The lung CT scans indicated that the most common manifestations were bilateral distribution of patchy shadows and ground glass opacity without pleural effusion. The lung CT results also indicated that the most severely affected patients were older.
Our analysis of laboratory data indicated the LY count was reduced in most patients, and that a greater chest CT score negatively correlated with LY count. This suggests that COVID-19 might act directly upon LYs, especially T LYs, as previously reported for SARS-CoV and MERS-CoV [18, 19]. Recent studies found that the severity of lymphopenia correlated with the severity of COVID-19 [20]. Our results indicated that the chest CT score had a positive correlation with the extent of lymphopenia. In agreement, a previous study reported that the semi-quantitative non-invasive chest CT score reliably predicted COVID-19 prognosis. As viruses spread through the respiratory mucosa and infect other cells, they induce a cytokine storm and a series of immune responses that cause changes in peripheral WBCs and immune cells. Coronviruses invade the lungs, as well as the blood, digestive system, and circulatory system [21–23]. Our analysis indicated that high chest CT score had a positive correlation with abnormal blood coagulation (based on measurements of PT and D-dimer), and severe cases are prone to fibrinolytic activation and excessive bleeding. This is consistent with the findings of Chen et al. [11]. However, we found no significant relationship of APTT level with chest CT score, suggesting that SARS-CoV-2 mainly affects the exogenous coagulation pathway.
Our analysis of chest CT scores of patients with COVID-19 indicated that the lesions were mainly at level 5, suggesting that the virus is most abundant in the more active parts of the lung. We also found that the initial chest CT score was positively correlated with the levels of systemic inflammatory factors (CRP and ESR). The overall radiologic score is based on the severity of air-space disease and its distribution. Previous studies found that patients who had viral pneumonias with consolidations evident in lung CT had more severe clinical courses than those who presented with ground glass opacities [24, 25]. These abnormalities also correlated with diffuse alveolar damage [26]. Patients who have COVID-19 and bilateral consolidations tended to have severe systemic inflammation. Because COVID-19 is an extremely contagious and potentially fatal disease, risk stratification using the simple chest CT scoring that we used here may help to appropriately triage patients, so that patients with more severe disease can receive more aggressive treatment and closer monitoring. In other words, the chest CT score should be considered for risk stratification of patients with COVID-19. However, use of initial chest CT scores for prediction of clinical outcome of patients with COVID-19 requires confirmation.
Further genetic, clinical, epidemiological, and clinical studies are needed to examine the efficacy of this semi-quantitative chest CT grading system to predict outcome, evaluate disease phenotypes, monitor disease progression, and evaluate treatment response and efficacy for other forms of viral pneumonia or air space diseases.
Due to the serious adverse effects of glucocorticoids experienced by patients with SARS-CoV infections [27, 28], it is questionable whether glucocorticoids should be used to treat patients with SARS-CoV-2 infections [29, 30]. Our results showed that patients who received glucocorticoids had greater improvements of chest CT score and LY count. This suggests that moderate application of glucocorticoids may have a positive effect in these patients. Our regression analysis indicated that the change of chest CT score after treatment had a positive correlation with the change in LY count, indicating that the chest CT score is useful in assessing patient status before and after treatment.
There were several limitations in this study. First, this was retrospective study and included only relatively small number of cases. All patients were reported to the CDC from January 2020 to February 202020 and required hospitalization, but were not admitted to the ICU. Therefore, the analysis was biased toward patients with more severe forms of COVID-19. However, the patients we examined were from the general ward, and none were admitted to the ICU. Therefore, many patients with COVID-19 have higher chest CT scores. Second, because we only examined five levels in the chest CT examinations, we may have missed some lesions. Last, because of time constraints, we only performed a cross-sectional study, and did not perform follow-up CT scans. All chest CT images were from patients at the time of admission and prior to treatment.
Some of the patients we examined progressed rapidly to ARDS, septic shock, and then multiple organ failure. Therefore, early identification and timely treatment of these critical cases is of crucial importance. The chest CT score is a non-invasive method that provides an actionable means for achieving this goal.