Forty-eight COVID-19 patients with complete medical records were included in the retrospective study, and all patients were in critical illness. According to the prognosis, the patients were classified into the non-survivor group and the survivor group, and the clinical characteristics of the two groups were statistically analyzed. There were 32 cases in the non-survivor group and 16 cases in the survivor group, all of which in the survivor group had been discharged at the end of the study data collection.
COVID-19 showed multiple risk factors confirmed in past documents (19-21). However, such factors may play different roles in certain stratifications of COVID-19 patients. Kaplan-Meier analysis was performed to identify differences between the survivor and non-survivor groups. As shown in Table 1, Log Rank method was used for Kaplan-Meier survival analysis of 42 variates. Variates Diabetes Mellitus, chronic obstructive pulmonary disease and family aggregation showed P values < 0.05, indicating their pivotal roles in mortality, while the others showed no significance. Furthermore, Table 2 confirmed significance of only Diabetes Mellitus, suggesting a more important role than those of the other two. Among the basic diseases of the two groups, the proportion of diabetes in the non-survivor group was significantly higher than that in the survivor group (P = 0.039). Intriguingly, the survivor group showed a higher rate of coronary heart disease than the non-survivor group. Apart from the two diseases, there was no statistical difference in other underlying diseases. Survival curve of variate DM, as shown in Fig. 1, suggested the mortality risk of diabetic patients was significantly higher than that of non-diabetic patients.
A retrospective study by Cao of early COVID-19 inpatients in Wuhan, China, found that elderly age, high D-dimer (greater than one ug/mL), and high SOFA score were high risk factors for patient mortality (7). The average age of the patients in the study was 67.5 years, including 71.5 years in the non-survivor group and 65.4 years in the survivor group. The patients included in our study were those in the late stage of the epidemic in Wuhan. The vast majority of patients included were old, which may be the reason for no statistical difference between the two groups. The CFR in this study was higher than that in the reference (22) (32/48 vs 836/1715, χ2 = 5.999, P = 0.014), which may be attributable to elderly age. The ranging CFR in different investigations may be explained by different patient traits, different organization, availability of ICU beds, and different lengths of follow-up (13, 16, 17, 22) . In Cao's study (7), the proportion of diabetes in the non-survivor group was 31%, and the survivor group was 14%. In univariable analysis, odds of in-hospital death were higher in patients with diabetes. The results were same as our study, suggesting that COVID-19 patients with diabetes should be fully paid attention to.
In our study, there was no significant difference in GCS, RASS and CAM-ICU scores between the two groups at the time of admission, and no statistical difference in blood test indicators such as leukocyte, hemoglobin, platelet, C-reaction protein and IL-6. Another retrospective study found that high troponin, high myoglobin, high C-reaction protein, and high IL-6 levels were likely predictors of death in COVID-19 patients (23). But the study did not detail the severity of the patients in survivor group. In our study, all patients enrolled were critically ill and ICU patients. C-reaction protein, IL-6, troponin, myoglobin, etc., were mostly at high levels in the survivor group and the non-survivor group, but only C-reaction protein, IL-2, IL-8, Creatinine and eGFR presented significant differences between the two groups. These results suggested these hematological indicators may not be sensitive enough to predict the risk of death in critically ill COVID-19 patients.
In conclusion, this study conducted a retrospective analysis of the clinical treatment of elderly and critically ill COVID-19 patients admitted to the single-center ICU, and found that diabetes was a more crucial factor for death, suggesting that full attention should be paid to the patients with diabetes in elderly critical COVID-19 patients. Although lower C-reaction protein, IL-2, IL-8, creatinine and higher eGFR were found in the non-survivor group than the survivor group, regular laboratory items could not serve as good predictors of death for elderly and critically ill COVID-19 patients admitted to ICU.