03.11 GI/GS
Liver function tests (LFTs)
Highly recommend reading the British Society of Gastroenterology guidelines – good summary of LFTs on p6 with references. Also GeekyMedics LFT interpretation.
Separate article on jaundice to follow soon (more studying needed T_T) – see GI/GS 03.12
ALT & AST
Enzymes found in liver cells; therefore raised when there is hepatocellular injury
E.g., hepatitis (due to various reasons), cirrhosis, malignancy
ALT more liver specific than AST
AST:ALT >2:1 is classically due to ArLD
ALP (alkaline phosphatase)
Enzyme produced in both biliary epithelial cells and bones; therefore raised in cholestasis or bone disease
Can be interpreted with GGT to help isolate source of raised ALP
If both ALP and GGT raised, cause likely due to cholestasis
If ALP raised but GGT normal, more in keeping with bone disease or other process going on
Circumstantial evidence for this but have been told by consultants before that ALP can be raised in infection. ALP is found in WCC (although brief lit search showed evidence from this from 1970s), which would give a theoretical basis for ALP rise in infection. However, there’s not much information on this on searching.
GGT (γ-glutamyltransferase)
Enzyme produced in both biliary epithelial cells and hepatocytes
Usually interpreted in conjunction with ALP; especially helpful in children where ALP would be raised physiologically due to bone growth
GGT rise tends to be associated with ArLD or obesity
Good predictor of liver mortality
Albumin
Produced only by the liver
Reduced albumin can be seen in liver disease
However, reduced levels can also be seen in other conditions such as sepsis/infection, nephrotic syndrome, malabsorption/malnutrition
Clotting function, esp INR
Clotting factors are produced by the liver – measure of INR indirectly measures liver function
Requires loss of >70% of liver synthetic function for rise in INR
Note as well though that INR can be affected by many other reasons eg warfarin, vitamin K deficiency, etc
Platelets
Thrombopoietin is produced by the liver and kidneys – platelet function can thus be reduced due to reduced liver function
However, platelet levels are also affected by many other factors
Note also platelet rise in infection
