Final answer:
The most likely cause of abnormal LFT on screening is liver disease, but LFT is not specific to the liver. Ratios of AST to ALT and elevated levels of ALP can provide additional information to differentiate between causes of liver damage. Increased levels of bilirubin can also indicate liver dysfunction.
Step-by-step explanation:
The most likely cause of abnormal liver function tests (LFT) on screening in a patient is liver disease. However, LFT is not specific to the liver as it is also present in red cells and cardiac and skeletal muscles. To differentiate between causes of liver damage, the ratio of AST (aspartate aminotransferase) to ALT (alanine aminotransferase) can be useful.
Alkaline phosphatase (ALP) is another enzyme that can indicate liver damage. Elevated ALP levels in plasma may indicate large bile duct obstruction, intrahepatic cholestasis, or infiltrative diseases of the liver. It should be noted that ALP is also present in bone and placental tissue, so higher levels can be seen in growing children and elderly patients with Paget's disease.
Increased levels of bilirubin, a yellow pigment found in bile, can cause jaundice which is often associated with liver dysfunction. However, an increase in bilirubin does not necessarily indicate liver damage but can suggest a problem with the liver's ability to process bilirubin. It is important to consult with a healthcare professional to determine the specific cause of the abnormal LFT.