Liver Function Tests (LFTs) are used for the ongoing monitoring of hepatitis C positive people. There are two aspects to liver function testing. The first is signs of liver injury. When liver cells are damaged or killed the enzymes, that exist inside the cell to do work, leak out into the blood stream. We can measure this. Because cells are dying and being replaced constantly, there is a little of the enzyme in your blood all the time. The amount present goes up when the liver is being injured by viral infection, toxic chemicals or alcohol, etc. These enzymes (known as transaminases) have a 'normal range'. It is only when the amount present exceeds the normal range that it clearly indicates ongoing liver damage. To complicate the issue, some people with normal liver enzymes (LFTs) also have ongoing damage. Signs of liver failure can also be observed through blood tests results.
ALT (Alanine-aminotransferate) is the marker of hepatitis C. In a hepatitis C positive person any elevation of ALT means active disease. Unfortunately the relationship between ALT and the amount of liver damage you have is weak, so you can have quite serious liver injury with only a mild elevation of ALT, or even a normal ALT reading There are three patterns of enzymes in hepatitis C virus, continually elevated readings, around 50 - 200 or so, fluctuating readings, when you have a blood test it may sometimes be normal and sometimes be elevated (for interferon treatment eligibility you need three elevated ALT tests within a six month period, to achieve this you can have blood tests done once or twice weekly if need be) and continuously normal. AST (aspartate aminotransferase) is often raised a little; usually lower than ALT. This has no particular significance.
GGT(gamma-glutamyl transpeptidase) is the liver enzyme that has been traditionally used as a marker of excess alcohol intake. If your GGT is up at all, you should consider giving up alcohol altogether whilst you are infected with hepatitis C. People with elevated GGT tend not to respond well to interferon. If GGT is over 100 or so, it can also be associated with gastro-intestinal symptoms (nausea, bloating, appetite disturbance and wind). Some people also have itching of the skin, the result of impairment to bile flow associated with bile duct damage, which is reflected in the elevated GGT. Your doctor can measure your bile acid levels and type on a regular blood specimen. These symptoms may be alleviated by the use of a medication called urso-deoxycholic acid (USDA), which is a 'friendly' bile acid and protects your bile ducts from ongoing damage. This medication is available on application to the 'special access drug scheme'. Your GP should discuss the matter with a liver specialist.
In routine hepatitis C all other liver tests should be normal. If you have abnormalities of liver production (that is the work side of your liver) then you are looking at liver failure and should be under a specialist who can work with your GP.
Other Blood Tests
Over 6 - 12 months you should have a number of other blood tests. These aim to screen you for other causes of liver disease; make sure you do not have; or are vaccinated against other liver toxic viruses; review your immune system, blood clotting and nutritional status.