The study population included 143 hospitalized patients with confirmed COVID-19. The median age was 58 years (IQR, 39-67; range, 14-84 years), and 73 (51.0%) were men. Of the 143 patients, 50 (35.0%) had 1 or more comorbidities. Hypertension (36 [25.2%]), cardiovascular disease (16 [11.2%]) and diabetes (13 [9.1%]) were the most common coexisting conditions. The most common symptoms at initial stage of illness were fever (137 [95.8%]), fatigue (93 [65.0%]), dry cough (78 [54.5%]), anorexia (66 [46.2%]), chest tightness (63 [44.1%]), myalgia (49 [34.3%]), mild shortness of breath (48 [33.6%]), chill (33 [23.1%]) and dyspnea (31 [21.7%]). Less common symptoms were nausea or vomiting, diarrhea and headache (Table 1).
Compared with mild/moderate group (n = 72), severe/critical group (n = 71) were significantly older (median age, 65 years [IQR, 53-69] vs 44 years [IQR, 32-60] ; P < 0.001) and were more likely to have underlying comorbidities, including hypertension (31 [43.7%] vs 5 [6.9%], and cardiovascular disease (12 [16.9%] vs 4 [5.6%]). Compared with the mild/moderate group, severe/critical group were more likely to report anorexia, expectoration, mild shortness of breath, dyspnea and myalgia.
There were numerous differences in laboratory findings between mild/moderate group and severe/critical group, including white blood cell, neutrophil counts, and lymphocyte count, as well as levels of high-density lipoprotein cholesterol (HDL-C), plasma glucose, serum potassium, total bilirubin (TBIL), albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), D-dimer, erythrocyte sedimentation rate (ESR), serum amyloid A (SAA), C-reactive protein (CRP) and procalcitonin (PCT) (Table 2).
Significant correlations were found about age, comorbidities, white blood cell count, neutrophil count, lymphocyte count, plasma glucose, serum potassium, albumin, D-dimer, HDL-C, TBIL, AST, ALT, LDH, ESR, SAA, CRP and PCT. Strikingly, this analysis revealed negative correlation between disease severity and lymphocyte count, albumin, serum potassium, and HDL-C (Table3). Age (r = 0.458), comorbidities (r = 0.445), LDH (r = 0.548), D-dimer (r = 0.477), SAA (r = 0.58), CRP (r = 0.477) were moderately correlated and albumin (r = -0.603) was highly correlated [[i]].
To better detect the severe illness, the ROC curve of age was administrated and listed in Figure 1A (AUC = 0.746, 95% CI: 0.686 - 0.831, P < 0.001). The best cut-off point of age was 52 years with a sensitivity of 76.1% and specificity of 63.9%. ROC curve of LDH (AUC = 0.816, 95% CI: 0.743 - 0.876, P < 0.001, Figure 1B) suggested the best cut-off point was 245 U/L with a specificity of 69.4 % and a sensitivity of 85.9%. ROC curve of D-dimer (AUC = 0.775, 95% CI: 0.698 - 0.841, P < 0.001, Figure 1C) suggested the best cut-off point was 0.96 ug/mL with 77.0% specificity and 78.1% sensitivity. ROC curve of SAA (AUC = 0.835, 95% CI: 0.764 - 0.892, P < 0.001, Figure 1D) indicated the best cut-off point was 100.02 mg/L with 72.2 % specificity and 85.9% sensitivity. ROC curve of albumin (AUC = 0.848, 95% CI: 0.779 - 0.903, P < 0.001, Figure 1E) indicated the best cut-off point was 36 g/L with a specificity of 83.3% and a sensitivity of 85.9%. ROC curve of CRP (AUC = 0.776, 95% CI: 0.698 - 0.841, P < 0.001, Figure 1F) suggested the best cut-off point was 64.79 mg/L with a specificity of 81.9% and a sensitivity of 64.8%.
As shown in Figure 2, the area under the ROC curve for albumin is the biggest, but it's not statistically significant. Binary logistic regression was applied to calculate the predictive probability of combined indicators for the speculation of disease severity. The combined indicators found that the AUC reached 0.921 (95% CI: 0.864 - 0.959, P < 0.001, Figure 3A), with a sensitivity of 87.3% and a specificity of 80.6%. The area difference between the combined indicators and albumin was 0.0726 (95% CI: 0.0125 - 0.133, P = 0.0179, Figure 3B), indicating that the accuracy of the combined identification of the six indicators was the best.