General clinical characteristics
In total, 142 consecutive patients with confirmed COVID-19 were included in this study. The mean age was 49.10±16.36 years, and 55 (38.73%) patients were men. Hypertension (37, 26.06%), diabetes (12, 8.45%), hepatic disease (10, 7.04%) and chronic lung disease (9, 6.34%) were the most common comorbidities. Fever (84, 59.15%) was the leading initial symptom, followed by cough (61, 42.96%), expectoration (32, 22.54%) and fatigue (27, 19.01%). In addition, 18 cases (12.68%) showed no obvious symptoms upon admission. All included patients received antiviral treatment. Moreover, 88 (61.97%), 53 (37.32%) and 52 (36.62%) patients were treated with gamma globulin, oxygen and antibiotics, respectively.
Among the 142 patients, 125 (88.03%) patients (19 mild and 106 moderate) were classified into the non-severe group, and 17 (11.97%) patients (14 severe and 3 critical) were included in the severe group. Significant differences in age (56.88±11.61 years vs. 48.04±16.66 years, P=0.010), body mass index (BMI) (26.13±5.47 kg/m2 vs. 23.50±3.42 kg/m2, P=0.007), hypertension (9 [52.94%] vs. 28 [22.40%], P=0.007) and fever (14 [82.35%] vs. 70 [56.00%], P=0.038) were noted between the severe and non-severe groups. Regarding clinical treatment, a greater proportion of patients in the severe group than the non-severe group received glucocorticoids, antibiotics, oxygen, invasive mechanical ventilation and intensive care unit treatment (Table 1).
Baseline laboratory parameters
The baseline laboratory parameters of patients were obtained within 5 days of admission. Compared with those in the non-severe group, patients in the severe group exhibited increased levels of neutrophil%, fibrinogen, activated partial thromboplastin time (aPTT), C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-10 (IL-10), interferon-γ (INF-γ), aspartate aminotransferase (AST) and lactic dehydrogenase (LDH), as well as reduced levels of lymphocyte%, lymphocyte count, platelet count, total cholesterol, HDL-C, LDL-C, ApoA1 and albumin (ALB). No significant differences in white blood cell (WBC) count, neutrophil count, red blood cell (RBC) count, haemoglobin, D-dimer, prothrombin time (PT), erythrocyte sedimentation rate (ESR), interleukin-2 (IL-2), interleukin-4 (IL-4), tumour necrosis factor-α (TNF-α), triglyceride, ApoB, lipoprotein (a), total bilirubin (TBil), direct bilirubin (DBIL), alanine aminotransferase (ALT), blood urea nitrogen (BUN), blood uric acid (BUA) or serum creatinine (Scr) were noted between the two groups (Table 2).
Risk factors of COVID-19 severity
Univariate logistic analysis showed that age, BMI, hypertension, neutrophil%, lymphocyte%, lymphocyte count, platelet count, fibrinogen, aPTT, CRP, IL-6, IL-10, HDL-C, ApoA1, ALB, AST and LDH were associated with the severity of COVID-19. However, only IL-6 (odds ratio [OR]: 1.097, 95% confidence interval [CI]: 1.034-1.165, P=0.002) and ApoA1 (OR: 0.865, 95% CI: 0.800-0.935, P<0.001) were recognized as independent risk factors by multivariate logistic analysis (Table 3).
A risk model was established using ApoA1 and IL-6. To predict the severity of COVID-19, the area under ROC curves (AUCs) for ApoA1, IL-6 and the risk model were 0.896 (95% CI: 0.834-0.941), 0.855 (95% CI: 0.786-0.908) and 0.977 (95% CI: 0.932-0.995), respectively (Figure 1, Table 4).
Correlation analyses showed that ApoA1 positively correlated with lymphocyte count (r=0.257, P=0.002), HDL-C (r=0.681, P<0.001) and ALB (r=0.412, P<0.001) but negatively correlated with fibrinogen (r=0.227, P=0.001), CRP (r=-0.337, P<0.001) and AST (r=-0.240, P=0.004). No correlations were found between ApoA1 and age, hypertension, neutrophil count, platelet count, IL-6, IL-10 and ALT (Figure 2).
Dynamic changes in ApoA1
Baseline ApoA1 levels in the severe group were significantly reduced compared with those in the non-severe group (P<0.001). ApoA1 levels in the severe group were increased during treatment (P<0.001); however, this trend was not observed in the non-severe group (P=0.223). In the recovery stage of COVID-19, no significant difference was noted between the two groups (P=0.560) (Figure 3).