SARS-CoV-2 and SARS-CoV are from the same species. To date, the prevalence rate and the deaths caused by COVID-19 have far exceeded those caused by SARS (severe acute respiratory syndrome) in 2003. As of 24:00 February 24, 2020, in China, there were77,658 cumulative confirmed COVID-19 cases, with 27,323 cured and2,663 deaths [6], for a mortality rate of approximately 3.4%.
Ten of the 13 patients (76.9%) who died were male, which was consistent with the results described in previous studies[7–10]. The average age of the deceased group was 74 ± 19, with 10 patients older than 70 years old (76.9%), higher than the ages of the patients in the moderate, severe, and critical groups. In the critical group, only 1 patient was older than 70 years (10.0%), indicating that the survival probability in patients older than 70 years old is very low once the disease progresses into the critical stage. No significant differences in clinical features were seen between the deceased group and the other 3 groups on admission, with primary symptoms of fever, fatigue and dry cough, as well as nausea, vomiting, abdominal pain and diarrhea observed in few patients, which is consistent with previous studies[11–12], indicating that patients with severe disease are rarely identified only by clinical manifestations at the early stage. Ten of the 13 patients who died had underlying diseases, with hypertension (53%) and coronary heart disease (23%) being the most common. Consistent with our study results, several previous studies showed that approximately 57.5% of patients with COVID-19 had at least 1 underlying disease, including hypertension, diabetes mellitus and/or cardiovascular disorders. Among them, the patients with underlying hypertension and heart disease were susceptible to progression into critical condition [13–15]. In our study, 6 patients in the deceased group had more than 2 underlying diseases (46.1%), significantly higher than that in the other 3 groups, indicating that COVID-19 patients with multiple chronic underlying diseases are at a higher risk of death.
On admission, the 13 patients all presented abnormal chest CT findings, with 8 (61.5%) exhibiting multiple patchy ground-glass opacities in both lungs, indicating that the wider the lesion area during the early state, the more possible a respiratory failure will occur with progression, which should draw clinical physicians’ attention. Notably, 4 out of the 13 patients who eventually died showed nonserious chest imaging abnormalities on admission characterized as a single ground-glass opacity, focal lesion or scattered thin ground-glass opacities in both lungs. However, repeated chest CT on days 3–6 after admission showed apparent progression characterized as an increase in ground-glass opacities and the emergence of patchy shadows with partial consolidation, progressing into diffuse lesions in both lungs on day9 ± 3 (mean) after admission, indicating that this disease progresses rapidly and that frequently repeated chest CT exams at the early stage are necessary.
As an essential part of the human immune system, cellular immune function plays a critical role in fighting viral infections by regulating and maintaining the ratio of T lymphocyte subsets. A study showed that 83.2% of COVID-19 patients presented lymphopenia on admission [16]. In a retrospective analysis of clinical data of COVID-19 patients, Guo et al.[15] showed that compared with the survival group, the deceased group had significantly decreased absolute counts of CD3+,CD4+, and CD8+T cells, indicating a correlation between cellular immune function and prognosis. In our study, the laboratory examination results showed that absolute peripheral blood lymphocyte counts and T lymphocyte subset counts in the deceased group at the early state were decreased and significantly lower than those in the other 3 groups, followed by a more substantial decrease as the disease progressed, with the lowest values obtained before death. One of the patients had an absolute lymphocyte count of 0.06 × 109/L before death. These results indicated that there is a relationship between the decrease in absolute peripheral blood lymphocyte counts and T lymphocytes subset counts as the severity increases. In addition, dynamic routine blood tests and T lymphocyte subset tests are predictors of disease progression and patient prognosis to a certain extent.
Even though normal human immune function can eliminate foreign microbiological matter, control infections and restore the body, viruses can elicit abnormal excessive immune responses and induce a substantial cytokine release by mononuclear macrophages and endothelial cells, thereby triggering a cytokine storm, resulting in serious injuries to organs and tissues [17]. Elevated serum levels of several inflammatory factors and C-reactive protein have been observed in COVID-19 patients, and the expression of inflammatory factors is related to disease severity[9, 18]. The pathological results show a large inflammatory cells count in organs and tissues throughout the whole body, indicating an apparent inflammatory response in COVID-19 patients [19]. In our study, IL-6, CRP, and D-dimer, the 3 commonly used inflammatory indicators in clinical practice, and lactic acid were selected for observation. Additionally, serum lactic acid, an important biochemical indicator of the body’s response to cell hypoxia and hemoperfusion, was used as a predictive measure of disease severity and patient prognosis. Our study found that all the indicators other than D-dimer in the deceased group were increased on admission. With disease progression, the levels of various inflammatory factors and lactic acid further increased, with a significant difference compared with the data on admission, until they peaked before death. These results indicate that there is a close correlation between the persistent excessive release of inflammatory factors and COVID-19 occurrence and progression, while persistent increasing serum lactic acid indicates persistent unimproved poor hemoperfusion. We found that even though IL-6, CRP and serum lactic acid showed different levels of increase in each group on admission, serum IL-6 was significantly higher in the deceased group than in the other 3 groups, in the following descending order: the critical group, severe group and moderate group. CRP and serum lactic acid showed nonsignificant differences among the various groups, indicating that IL-6 might be a more sensitive indicator of disease severity than other inflammatory factors and that dynamic monitoring of IL-6, CRP, D-dimer and lactic acid levels might be more valuable in predicting patient prognosis.