Liver function tests at admission could help predict mortality from COVID-19

Elevations in aspartate aminotransferase and direct bilirubin levels were significantly more common among patients in China who died of COVID-19 than those who survived to hospital discharge, a retrospective study found.

Abnormal liver function was common among hospitalized COVID-19 patients in a recent study, and aspartate aminotransferase (AST) and direct bilirubin levels were particularly predictive of mortality.

The retrospective study included 2,073 patients hospitalized with COVID-19 in Wuhan, China, about 10% with pre-existing liver disease (including 134 with hepatitis B). Overall, 61.8% had abnormal liver chemistries during hospitalization, and 14.3% had a liver injury. Of 200 patients who died, 73.0% had liver abnormalities at admission, compared to 43.4% of those who survived to discharge (P<0.001). Results were published by the Journal of Hepatology on Dec. 18, 2020.

The researchers also looked at the association of specific liver function tests with inpatient mortality. In patients who died, the mean levels of AST and direct bilirubin increased early after symptom onset and differed from those in patients surviving to discharge. Elevations in AST were relatively common (38.9% during hospitalization and 26.3% at admission), whereas direct bilirubin elevation was more unusual, found in 9% of all patients at admission but 33% of those who died. Abnormal admission levels of either were found to be independent risk factors for death from COVID-19 (adjusted hazard ratios, 1.39 [95% CI, 1.04 to 1.86] for AST and 1.66 [95% CI, 1.22 to 2.26] for direct bilirubin; P=0.027 and P=0.001, respectively). Hepatitis B infection was not associated with any increase in risk of poor outcomes associated with COVID-19.

The authors concluded that monitoring liver chemistries, especially AST and direct bilirubin levels, is necessary in hospitalized patients with COVID-19. They highlighted the additional finding that “[A]bnormal D-Bil [direct bilirubin] is commonly found during the hospital stay of deceased patients with COVID-19, with its prevalence second only to that of abnormal AST level in liver chemistries, despite the fact that abnormal D-Bil levels are not commonly found in patients with COVID-19.” The authors also noted that the patients who developed liver failure all had acute injuries in other organs as well. “These results suggest that the liver is unlikely a key organ driving the mortality due to COVID-19, although liver abnormalities are commonly found in COVID-19,” they said.

Limitations of the study include its retrospective design, which meant that the causality of the findings could not be determined. The authors called for future studies to evaluate the observed association between early AST and direct bilirubin elevation and mortality in patients with COVID-19.