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Journal of Clinical Medicine Research

Original Article

Volume 13, Number 5, May 2021, pages 258-267

Low Serum Albumin Predicts Severe Outcomes in COVID-19 Infection: A Single-Center Retrospective Case-Control Study

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a novel viral disease first discovered in December 2019 in Wuhan, China. Within 1 month, it was confirmed in 19 countries [1] and the World Health Organization declared it a pandemic shortly thereafter [2]. As of now, it has been established as a highly contagious viral disease, primarily affecting the respiratory system but with complications including kidney injury, liver injury, cardiac injury, stroke, encephalopathy, post-viral debility, coagulopathy, long hospital stay, and significant risk of mortality [3-12]. The majority of the patients survive the infection without complications, but a notable proportion of patients develop serious complications. Since the beginning, high levels of acute inflammatory markers were observed in the patients who had poor outcomes but the factors that lead to serious complications remain inadequately understood [3-5].

Albumin serves as a major anti-inflammatory agent in our body [13, 14], and one of the lesser discussed properties in the literature are its anti-oxidative and anti-thrombotic property [15, 16]. Albumin is a major defense that protects the host cells from the oxidative burst that occurs against the infection or inflammation [17-19]. Albumin has a long half-life (3 weeks) and 90% of it is in plasma [20]. The level of plasma is dropped rapidly during acute inflammation due to transcapillary leakage, consumption, and other mechanisms [13, 19, 21, 22].

As of now, we lack proven and effective therapeutic options to treat serious complications of COVID-19 infection. We also lack the ability to predict the serious outcomes of COVID-19 infection. In many studies, low levels of albumin, in addition to high inflammatory markers had been observed with those patients that had poor outcomes. Some studies have suggested that low serum albumin can predict mortality in COVID-19 infection [23-27].

We conducted this study to explore this relationship further with the hypothesis that low serum albumin at presentation can predict serious outcomes in COVID-19 infection.

The study was approved by Cape Fear Valley Medical Center’s Institutional Review Board (IRB ID number 319-20). This study was conducted in compliance with the ethical standards of the IRB on human subjects.

The study was a single-center retrospective case-control study. We reviewed the charts of patients with the discharge diagnosis of “COVID-19, virus identified” (ICD code U07.1) from March 1 to July 31, 2020 in a tertiary care center in North Carolina, United States of America (USA). We identified 796 charts that had confirmed SARS-CoV-2 reverse transcriptase-polymerase chain reaction (RT-PCR) results of nasopharyngeal swab. After exclusions, a total of 352 charts of unique patients were included in the study (Fig. 1). Inclusion criteria included: 1) patients with SARS-CoV-2 detected using the RT-PCR method, 2) age 18 and above, and 3) admission date between March 1, 2020 and July 31, 2020. Patients with 1) emergency department (ED) visits only, 2) less than 18 years of age, 3) pregnancy, and 4) no serum albumin available at presentation in the ED were excluded (Fig. 1).

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Figure 1. Flow diagram of eligible patient selection. RT-PCR: reverse transcriptase polymerase chain reaction; SARS-CoV-2: severe respiratory syndrome coronavirus 2.

Included patients were classified into two groups based on serum albumin at presentation: normal serum albumin (NSA) group with a value of ≥ 3.5 g/dL, and low serum albumin (LSA) group < 3.5 g/dL. The low albumin group was further sub-grouped as mild low albumin (MLA) group with a value of 2.5 - 3.4 g/dL and very low albumin (VLA) group with a value of < 2.5 g/dL for subgroup analysis. The patients were followed up for 21 days or until death if it happened sooner.

The primary outcome was defined as a composite outcome of death or any serious complications. The variables of serious complications were death, acute encephalopathy, acute kidney injury, the requirement of new renal replacement therapy, acute hypercoagulability, acute circulatory failure, new-onset heart failure, acute cardiac injury, acute arrhythmia, acute respiratory distress syndrome (ARDS), high flow oxygen support, intensive care unit (ICU) stay, and mechanical ventilation. The study definitions and definitions of serious complications are outlined in Table 1. The secondary outcome was death due to any cause during the 21 days follow-up period. The abbreviations, normal ranges, and units of variables are outlined in Table 2.

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Table 1. Study Definition

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Table 2. Abbreviations, Normal Ranges and Units

A formal sample size calculation was not carried out as all patients meeting criteria in the pre-specified timeframe were included. The differences in categorical variables were analyzed using a Chi-square test, or Fisher’s exact test as appropriate. A Student’s t-test was utilized to evaluate differences in continuous variables that were normally distributed, and a Wilcoxon rank sum test was utilized if the data were not normally distributed. Continuous variables were expressed as mean ± SD and categorical variables were expressed as the frequency with percentages. The association of albumin level category and outcome was estimated in univariate and multivariate logistic regression analyses in terms of odds ratio (OR). Multivariate analyses were adjusted for age, sex, race, diabetes mellitus (DM), hypertension (HTN), chronic kidney disease (CKD), end-stage renal disease on hemodialysis (ESRD on HD), chronic obstructive pulmonary disease (COPD), other lung diseases, congestive heart failure (CHF), coronary artery disease (CAD), human immunodeficiency virus (HIV) infection, malignancy, smoking, alcohol dependency, obesity, and cirrhosis. A P-value of < 0.05 was considered significant. Data analysis was performed using STATA 13.1 (Stata Corp., College Station, TX).

Baseline demographic and lab characteristics by albumin level categories are depicted in Table 3. The overall population was predominantly males (n = 184, 52.27%), and African-American (n = 176, 50%). Eighty-one percentage (n = 288) had at least one co-morbidity. Cough (62.78% vs. 73.81%, P = 0.16), fever (58.90% vs. 64.29%, P = 0.5), and shortness of breath (64.08% vs. 59.52%, P = 0.56) were the most common presenting symptoms in the LSA and NSA groups, respectively. The frequency of CKD was higher among the NSA group (35.71% vs. 17.10%, P < 0.05). Among the subgroups of low albumin, the presenting symptoms and co-morbidities were similar between the two groups (Table 3).

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Table 3. Baseline Characteristics of Normal and Low Serum Albumin Groups

The LSA group had a significantly higher proportion of composite outcome compared to the NSA group (93.88% vs. 6.12%, P < 0.05). This difference was true in between the subgroups of only low albumin as well, where 96.72% of the VLA group had composite outcome as compared to 81.12% in the MLA group (P < 0.05) (Table 4).

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Table 4. In-Hospital Complications and Duration of Stays in Normal and Low Serum Albumin Groups

Logistic regression analysis revealed higher odds of having composite outcome with the lower albumin group during univariate (OR 7.83, 95% confidence interval (CI) 3.94 - 15.58, P < 0.05) and multivariate (OR 10.88, 95% CI 4.74 - 24.97, P < 0.05) analyses. Subgroup analysis also revealed a similar relationship (Table 5).

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Table 5. Results From Logistic Regression Analyses - Odds of Composite Outcome Based on Albumin Level Category

In comparison to the NSA group, the LSA group had higher length of stay (9.33 days vs. 4.48 days, P < 0.05), higher incidence of acute kidney injury (AKI) (42.90% vs. 14.29%, P < 0.05), acute encephalopathy (22.90% vs. 7.14%, P < 0.05), mechanical ventilation use (13.23% vs. 2.38%, P < 0.05), development of ARDS (19.35% vs. 2.39%, P < 0.05) and post-viral physical debility (24.19% vs. 3%, P < 0.05). Similar differences were observed between the VLA and MLA groups with a higher incidence among the VLA group (Table 4). Multivariate analysis revealed that malignancy had the strongest influence on the primary outcome (OR 11.34, 95% CI 2.05 - 62.64, P < 0.05) (Table 6).

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Table 6. Results From MV Analysis in Normal and Low Albumin Groups

The LSA group was found to have higher mortality within 21 days as compared to the NSA group (13.87% vs. 2.38%, P < 0.05). Subgroup analysis of the low albumin group revealed 31.15% mortality in the VLA group vs. 9.64% in the MLA group (P < 0.05) (Table 4). We were unable to perform the regression analysis on mortality outcomes due to the very low number of mortalities in the normal albumin group.

In this single-center study, we found that low serum albumin at the presentation in hospitalized patients with COVID-19 infection predicted higher mortality. Lower serum albumin at presentation was found to be an independent predictor of serious outcomes even after controlling for the multitude of factors such as age, sex, and presence of co-morbid conditions.

Low albumin level has been reported in hospitalized patients with COVID-19 that had poor outcomes from the beginning of the pandemic [3-5, 28]. A similar trend was observed in other studies that were conducted outside of China as well [26, 27, 29]. A few studies that compared low albumin level with mortality concluded that low albumin can predict mortality in COVID-19 patients [23-25]. In addition to low albumin, high levels of inflammatory markers were also noted in those studies. The findings of our study are consistent with these prior findings.

Low albumin has been found to predict higher mortality, a longer length of stay in hospitalized patients, and the general elderly population [30-34]; normalization of albumin prior to discharge was found to lower the mortality [33]. Albumin therapy has been shown to improve the oxygenation in ARDS [35, 36], and improve mortality in spontaneous bacterial peritonitis patients [37]. In the letter to the editor by Wiedermann et al and its response, the authors reported pooled analysis of three large-scale randomized controlled trials on sepsis and found that albumin therapy had a significant reduction in mortality which was attributed partly to albumin’s anti-oxidative and anti-immunosuppressive property [38]. The mechanistic theory for this includes albumin’s ability to bind reactive oxygen and reactive nitrogen species (ROS and RNS) preventing cellular damage and tissue injury during overwhelming inflammatory response [17-19]. These findings have given rise to the concept of the potential therapeutic use of albumin for COVID-19 infection [27, 39].

One of the limitations of our study is being a single-center study. More than 50% of the charts needed to be excluded decreasing the sample size. However, our study sample size was comparable to many similar studies done recently. The population was of mixed races unlike many studies done in China or Europe. We could not do the multivariate analysis of mortality because there was only one death in the normal albumin group.

COVID-19 has been diagnosed in more than 200 countries [40]. In the USA alone more than 30 million people were infected, and 556 thousand had died [41]. So far, there is no effective treatment for COVID-19 infection [40, 42-47], and the success of developed vaccines being unanswered due to emerging new strains of SARS-CoV-2. Due to recurrent waves of infection caused by emerging strains of SARS-CoV-2 the South Asian region, South American, Europe and other parts of the world had been through series of lockdowns. In addition, the vaccines are still out of reach of many low-medium income countries. We believe that this study will help health providers recognize that lower albumin carries a higher risk of severe complications and mortality in COVID-19 infection. It will be interesting to see the studies that utilize albumin as a treatment for serious COVID-19 illness.

Low serum albumin on presentation in COVID-19 infection is associated with a higher incidence of serious outcomes like kidney injury, cardiac injury, hypercoagulability, post-viral physical debility, and encephalopathy; and higher mortality. Further investigation of the utility of albumin replacement as a treatment of COVID-19 infection should be done as soon as possible.

Acknowledgments

None to declare.

Financial Disclosure

None to declare.

Conflict of Interest

None to declare.

Informed Consent

The informed consent was waived by IRB as the study was a retrospective study.

Author Contributions

RA designed the study, portions of statistical analysis, manuscript writing; DP and RB did the statistical analysis and contributed to manuscript writing; RA, AP, ES, MB, RP, SS, MB and SK did the portions of statistical analysis, and contributed to manuscript writing; KL and IL contributed to manuscript writing and supervision of the study. All authors read and approved the final manuscript.

Data Availability

The database used and/or analyzed during the current study is available from the corresponding author on reasonable request.

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