High aspartate aminotransferase to alanine aminotransferase ratio on admission as risk factor for poor prognosis in COVID-19 patients

This study aimed to analyze aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio in COVID-19 patients. After exclusion, 567 inpatients were included in this study and separated into two groups according to their AST/ALT ratio on admission. Death was regarded as poor prognosis in this study. Of 567 patients, 200 (35.3%) had AST/ALT ≥ 1.38. Of the 200 patients, older age (median age 60 years), myalgia (64 [32%] cases), fatigue (91 [45.5%] cases), some comorbidities and outcomes were significantly different from patients with AST/ALT < 1.38. They also had worse chest computed tomography (CT) findings, laboratory results and severity scores. Levels of platelet count (OR 0.995, 95% CI [0.992–0.998]) and hemoglobin (OR 0.984, 95% CI [0.972–0.995]) were independently associated with AST/ALT ≥ 1.38 on admission. Furthermore, a high AST/ALT ratio on admission was an independent risk factor for poor prognosis (OR 99.9, 95% CI [2.1–4280.5]). In subsequent monitoring, both survivors and non-survivors showed decreased AST/ALT ratio during hospitalization. In conclusion, high AST/ALT ratio might be the indication of worse status and outcomes in COVID-19 patients.

Elevated AST/ALT ratio on admission indicates poor prognosis as an independent risk factor. Of the 567 included patients, 490 (86.4%) of them recovered and were discharged after comprehensive clinical assessment of symptoms, chest CT and viral clearance; 65 (11.5%) patients died during hospitalization; 12 (2.1%) patients with unknown outcomes were transfer to other specialized hospitals due to deterioration. To analyze the risk factors of biochemical findings on poor prognosis, we performed logistic regression analysis in 555 patients with clear survival information (recovery or death) ( To assess independent risk factors for poor prognosis, we performed logistic regression analysis on liver enzymes and other biochemical parameters. However, collinearity was significant among BUN, creatinine, white blood cell count and neutrophil count (VIF = 7.8, 8.2, 18.7 and 18.2, respectively). Therefore, we performed Spearman's rank correlation analysis in order to select variables and reduce collinearity. BUN and neutrophil count had higher correlation coefficients than creatinine (0.34 vs 0.25) and white blood cell count (0.18 vs 0.11), respectively. Therefore, creatinine and white blood cell count were excluded from the subsequent multivariate logistical regression. In multivariate analysis, high AST/ALT ratio (adjusted OR 99.  (Table 4).
To assess the AST/ALT ratio on poor prognosis of patients with different liver enzyme levels 23 , we separated the 555 COVID-19 patients with clear survival data (recovery or death) into two groups according to their AST levels (≤ 40 or > 40 U/L) on admission (Table 5). Of the patients with normal liver enzyme levels and AST/ALT < 1.38 (n = 295), 17 (5.8%) patients had poor prognosis, while of the patients with AST/ALT ≥ 1.38 (n = 157), 28 (17.8%) patients had poor prognosis (OR 3.5; 95% CI [1.9-6.7]; P < 0.001). Of the patients with AST levels > 40 U/L and AST/ALT < 1.38 (n = 65), 7 (10.8%) patients had poor prognosis, while of the patients with Table 3. Multivariate analysis of AST/ALT ≥ 1.38. *A two-tailed P value less than 0.05 was considered statistically significant.

Laboratory parameters
Multivariable OR (95% CI) P Value  (Table 5). Therefore, AST/ALT ≥ 1.38 was a risk factor for poor prognosis in both groups of patients with different AST levels (≤ 40 or > 40 U/L).

Monitoring AST/ALT ratio during hospitalization. Most patients also received liver enzyme tests on
other hospital days (days 3, 7 and 14) in addition to on the day of admission according to their clinical care needs. In discharged patients with recovery, their AST/ALT ratio significantly decreased during hospitalization ( Fig. 2A). Similarly, the AST/ALT ratio of patients with poor prognosis also decreased noticeably from day 1 to day 3. From day 3 to day 14, the AST/ALT ratio also tended to decrease, but there was no statistical significance (Fig. 2B).

Discussion
Among a variety of recent publications about COVID-19, accumulated evidence suggests that SARS-CoV-2 infections might cause multiple and systemic injuries, including acute renal failure, myocardial dysfunction, and acute liver injury 23,25,26 . Additionally, there are recent studies analyzing COVID-19 patients in detail with respect to liver Table 4. Univariate and multivariate analysis on poor prognosis (Death). Patients with clear survival data (recovery and death) were enrolled in the analysis on prognosis (N = 555). # Variance inflation factor (VIF) > 5 was considered collinearity. *A two-tailed P value less than 0.05 was considered statistically significant.  Table 5. Univariate analysis of the AST/ALT ratio on poor prognosis in the two groups of patients. Values are numbers (percentages) unless stated otherwise. Patients with clear survival data (recovery and death) were enrolled in the analysis on prognosis (N = 555). *A two-tailed P value less than 0.05 was considered statistically significant.  www.nature.com/scientificreports/ enzymes, such as ALT and AST 23,27 . The underlying mechanism of elevated liver enzymes in COVID-19 patients remains unclear. Additionally, the relationship between COVID-19 and AST/ALT ratio was still not revealed.

Outcomes
In this study, we described COVID-19 patients admitted with different AST/ALT ratio, we found that a high AST/ALT ratio was a risk factor for poor prognosis and monitored changes in AST/ALT ratio during hospitalization. Older COVID-19 patients had a higher case fatality rate 28 . Similarly, having comorbidities might also contribute to worse outcomes 29 . In this study, there was a higher proportion of older and comorbid patients with AST/ALT ≥ 1.38. COPD, cardiovascular, chronic kidney diseases were the most significant coexisting diseases among the 6 comorbidities of patients with AST/ALT ≥ 1.38 on admission. Interestingly, they also preferred to have more than one comorbidity, which might be related with their worse status. Additionally, patients with AST/ALT ≥ 1.38 on admission were also likely to have poor prognosis (death). Therefore, liver tests on elderly COVID-19 patients with myalgia, fatigue and ≥ 2 comorbidities are necessary on admission.
The relationship between AST/ALT ratio and other laboratory findings in COVID-19 patients is unclear. This study described massive differences in laboratory parameters between the two groups of patients. Patients with AST/ALT ≥ 1.38 had lower hemoglobin, lymphocyte and platelet counts, which might be related to the disease severity 30,31 . As previous reports, increased white blood cell counts also indicated patients with severe COVID-19 30,32 . However, our results suggested that patients with AST/ALT ≥ 1.38 were likely to have lower white blood cell counts, which seems to be against previous reports. Interestingly, when compared the white blood cell counts between survivors and non-survivors in our study, patients with poor prognosis indeed had higher white blood cell counts (median number, 6.02 × 10 9 /L [IQR, 3.7-9.4] vs 4.8 × 10 9 /L [IQR, 3.7-6.2]; P = 0.01). Therefore, the relationship between AST/ALT ratio and white blood cell counts remains further research.
Furthermore, compared with patients with AST/ALT < 1.38, those patients with AST/ALT ≥ 1.38 were also susceptible to have worse myocardial function (higher LDH and CK-MB levels) and more severe systemic inflammation (higher CRP and procalcitonin levels). In general, AST/ALT ≥ 1.38 might indicate that the patients were suffering from more intensive systemic injuries. In addition, more severe chest CT results (showing a larger proportion of lesions in the lung), worse blood gas analysis (lower PaO 2 /FiO 2 ) and higher severity of illness scores (higher APACHE II, SOFA and CURB-65) were also more frequent in patients with AST/ALT ≥ 1.38. Importantly, a higher SOFA score have been recommended as indictors for worse outcomes in early COVID-19 patients 15 . Moreover, in multivariate analysis, lower levels of hemoglobin and platelet count were independently associated with AST/ALT ≥ 1.38.
Additionally, the AST/ALT ratio was found to be a risk factor for death in both groups of COVID-19 patients with normal or abnormal AST levels. Besides that, the AST/ALT ratio, for unclear reasons, has some extrahepatic implications, including predicting poor outcomes of pancreatic cancer patients 33 and heart injury in Kawasaki disease 34 . Therefore, the role of the AST/ALT ratio in COVID-19 remains to be further analyzed. We also monitored the dynamic AST/ALT ratio during hospitalization. The AST/ALT ratio tended to decrease during hospitalization in both two groups patients with distinct outcomes. Therefore, high AST/ALT ratio in COVID-19 patients might be eased to a large extent after receiving medical treatment. However, the AST/ALT ratio in patients with recovery showed more sustained reduction. Therefore, after day 3, continuously decreased AST/ ALT ratio might indicate good prognosis in COVID-19 patients. Future studies on the dynamic changes of AST/ ALT ratio in COVID-19 are expected.
In summary, our results suggested that older COVID-19 patients with myalgia, fatigue, or ≥ 2 coexisting diseases were more likely to have AST/ALT ≥ 1.38 on admission. We also provided evidence that AST/ALT ≥ 1.38 was significantly associated with more severe chest CT findings, worse laboratory results, higher severity of illness www.nature.com/scientificreports/ scores, and poor prognosis as an independent risk factor of COVID-19 patients. Therefore, it is necessary to provide advanced medical care to COVID-19 patients with AST/ALT ≥ 1.38 on admission. Statistics. Receiver operating curve (ROC) was utilized to compare the effects of different clinical indexes in predicting prognosis and find out cut-off value. Kaplan-Meier survival analysis was employed to show the outcome of COVID-19 patients. We described the categorical variables as numbers with percentages and continuous variables as medians with interquartile range (IQR) values. Categorical variables and count data were compared using the Chi-square tests, and Continuous correction chi-squared tests was performed if relevant data were limited. Normally distributed data of continuous variables were compared using independent group t-tests; when the data were not normally distributed, Mann-Whitney U tests were performed. Furthermore, univariate and multivariate logistic regression analysis was performed after collinearity diagnostics. A variance inflation factor (VIF) greater than 5 was considered significant collinearity. Spearman's rank correlation analysis was performed to select variables for further multivariate analysis. Paired Wilcoxon's tests were performed to compare the AST/ALT ratio on different hospitalization days. All data were statistically analyzed using SPSS software, version 25.0. In this study, a two-tailed P value less than 0.05 was considered statistically significant.

Study design and patients.
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