2.1 Characters of patients
All detections for the COVID-19 patients were conducted at Shandong First Medical University Affiliated Provincial Hospital, Tengzhou Traditional Chinese Medical Hospital and Tengzhou Central People’s Hospital in China. The research protocol was reviewed and approved by Shandong First Medical University Affiliated Provincial Hospital, and Tengzhou Traditional Chinese Medical Hospital and Tengzhou Central People’s Hospital. Eligible participants were healthy adults aged 60 years or older. Individuals who had a history of COVID-19 or were tested positive for SARS-CoV-2 exposure, or who had been in contacted with confirmed COVID-19 patients were included. Eligible older participants were required to be generally healthy and 60 to 96 years of age. General health, assessed during the screening period, was based on clinical laboratory findings, vital signs, physical examination and medical history. The male-to-female ratio was higher in all four groups of enrolled patients, but the difference in gender composition between the groups was not statistically significant (P > 0.05). Similarly, there was no statistically significant difference in average age (P > 0.05) or disease duration (P > 0.05) among the groups. Power analysis show that sample size in this study can guarantee 90% confidence in obtaining statistical difference (b=0.9,α=0.05, period=12 months).Therefore, the groups are considered comparable (Table 1).
2.2 Study design and sample collection
In total, 162 blood samples of COVID-19 patients in the Hospital as described in materials and methods were collected (Figure 1). The samples were transported to the laboratory and processed for some analyses. Blood routine examination was conducted by Count Coulter auto-hemocyte analysis instrument. Meanwhile, 44 biochemical parameters were also systematically detected and analyzed in the serum of COVID-19 patients.
2.3 Correlation between anemia and the severity of COVID-19, albumin and the severity of COVID-19
According to the measurement of hemoglobin, patients were divided into two groups: normal control (>120 g/L ) and anemice (≤ 120 g/L ). A statistical test was conducted to examine the association between anemia status and the severity of COVID-19 using an ordered logistic regression analysis. The p-value obtained was 0.0657, which is greater than 0.05, indicating that there is no significant correlation between the two groups. According to the measurement of hemoglobin, the severity of anemia is divided into three levels: mild group (90-120g/L), moderate (60-90 g/L), and severe (30-60 g/L). A statistical test was conducted to examine the association between the severity of anemia and the severity of COVID-19 using Fisher's chi-square test. The obtained p-value was 0.217, which is greater than 0.05, indicating that there is no significant correlation between the two. According to the measurement values of albumin, patients with albumin level ³ 35 g/L are classified as normal, while those with albumin level < 35 g/L are classified as having hypoalbuminemia. A statistical test was conducted to examine the relationship between the presence of hypoalbuminemia and the severity of COVID-19, using ordered logistic regression analysis. The obtained p-value was 1.24e-06 < 0.05, indicating a significant correlation between the two factors. A correlation analysis was also performed, and the Spearman correlation coefficient was found to be 0.3856727, indicating a moderate positive correlation between the presence of hypoalbuminemia and the severity of COVID-19. According to the measurement values of albumin, hypoalbuminemia is classified into three levels: mild, moderate, and severe. mild hypoalbuminemia group (30-35 g/L); moderate hypoalbuminemia group (25-29 g/L); and severe hypoalbuminemia group (<25 g/L). A statistical test was conducted to examine the relationship between the severity of hypoalbuminemia and the severity of COVID-19, using Fisher's chi-square test. The obtained p-value was 0.3382 > 0.05, indicating that there is no significant correlation between the two factors (Table 2, Figure 2A, 2B).
2.4 Correlation between anemia and patient outcomes, albumin and patient outcomes
A statistical test was conducted to examine the correlation between anemia in patients and patient outcomes using the chi-square test. The obtained p-value was 0.03204, which is less than 0.05, indicating a significant correlation between the two factors. Further correlation analysis using Spearman's correlation coefficient revealed a coefficient of 0.1622748, indicating a positive weak correlation. This suggests that there is a positive correlation between patients with anemia and mortality rate. A statistical test was conducted to examine the correlation between the severity of anemia in patients and patient outcomes using the Cochran-Armitage trend test. The obtained p-value was 0.5186, which is greater than 0.05, indicating that there is no significant correlation between the two factors. The statistical test conducted examined the relationship between whether patients had hypoalbuminemia and patient outcomes using the chi-square test. The obtained p-value was 3.028e-05 < 0.05, indicating a significant correlation between the two factors. A correlation analysis was performed, and the Spearman correlation coefficient was 0.3035322, indicating a moderate positive correlation. Patients with hypoalbuminemia were positively correlated with mortality rate. The statistical test conducted examined the relationship between the severity of hypoalbuminemia in patients and patient outcomes using the Cochran-Armitage trend test. The obtained p-value was 0.03032, indicating a significant correlation between the two factors. In the correlation analysis, the Spearman correlation coefficient was 0.2100583, indicating a positive correlation between different degrees of hypoalbuminemia and patient mortality rate (Table 2, Figure 3).