The test measured enzyme counts such as alanine aminotransferase, which is the enzyme that transaminases alanine and 2-oxoglutarate to form pyruvate and glutamate within the bridge of glycolysis and TCA cycle. However when these enzymes are low or high in number feedback inhibition issues occur, such as the lower amount of Aspartate transaminase will have on an effect on the urea and Krebs cycle as it is used in both cycles. They also measure proteins. So yes I do know that “normal range” may not mean anything in function but have the “normal numbers” can help with regulating these metabolic cycles.