Which laboratory test is the best indicator of liver function?

Prothrombin time (PT) is a critical laboratory test that reflects liver function, particularly its synthetic capacity. The liver is responsible for producing several clotting factors, and PT measures the time it takes for blood to clot, which is primarily dependent on the coagulation factors II, V, VII, and X. These factors are synthesized in the liver, and any significant impairment of liver function can lead to prolonged PT.

In contrast, while ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are both enzymes found in the liver that indicate hepatocellular injury, they do not provide direct insight into the liver's synthetic function. Elevated levels of these enzymes may reflect liver damage but do not necessarily correlate with the overall functional capacity of the liver in synthesizing proteins such as those required for coagulation.

Albumin levels are another important measure related to liver function, as albumin is produced by the liver, and low levels can indicate liver dysfunction. However, albumin levels can be influenced by other factors such as nutritional status and kidney function, making it less specific than PT for assessing liver synthetic capability.

Thus, among these options, PT is the best indicator of liver function as it directly reflects the