Liver injury in COVID‐19: Diagnosis and associated factors

We read with interest the study by Xie et al about the liver injury in non-ICU hospitalized COVID-19 patients1; the authors found liver injury was prevalent in COVID-19 patients and might associate with CT scores. However, we believe some concerns should be aroused regarding this conclusion. Liver function abnormalities were frequent in COVID-19 patients, especially the severe cases.2 However, as a new contagious disease, there is no standardized diagnostic criteria of COVID-19–associated liver injury at present. Some researchers defined liver injury as any liver function parameter above the upper limit of normal (ULN),3 but others defined it as liver enzymes higher than two or three times of ULN, and even further classified different liver injury patterns.4 This study defined elevated levels of alanine transaminase (ALT), aspartate aminotransferase (AST) or bilirubin as liver injury without specifying the ULN of laboratory reference, which was ambiguous and made it difficult to replicate their results. Furthermore, the time point of diagnosing liver injury was vague. Although we can infer this diagnosis of liver injury was made on the initial laboratory tests on the admission throughout the paper, the authors did not directly mention it. Similarly, the time point of post-treatment was unclear. The authors described post-treatment ALT and AST levels, however, the exact day (i.e. the 1st, 3rd or 7th day after treatment) was unknown, and the time interval may affect the level of liver enzymes. Also, it was unclear whether the post-treatment data came from a single test or from the average of multiple post-treatment tests. Efforts should be made to establish a standardized definition and diagnostic time point of liver injury in COVID-19 patients. Another important finding in this study was that severe lung lesions on CT (i.e. high CT score) might be related to higher incidence of liver injury. However, the CT scores were assigned on the basis of the percentage of involved lung area, which was semi-quantitative and subjective. Quantification of lung involvements with advanced CT post-processing software or AI algorithms may be more accurate and reproducible.5 Moreover, although CT score was suggested an independent predictor for liver injury in COVID-19 patients, it remains unclear that how many variables were included in the logistic regression and whether the CT score was the only significant predictor. In summary, this study provided interesting but preliminary findings. Large-sample multicentre studies are needed to validate these results and further explore COVID-19–associated liver injury.