These are exactly what they suggest, a number of tests that look at how the liver is functioning. There are a number of markers in the blood that can be measured to help gauge the state of the liver. They are relevant for all types of hepatitis. None of them, either individually or in conjunction, can provide a perfect picture of the state of a person’s liver, merely some indications. Only a few are described here. However by far the best way to get an idea of how healthy or unhealthy a liver is to take a piece of it and look at it under the microscope. This procedure is called a liver biopsy.

The most important liver function tests are for ALT (alanine aminotransferase) and AST (aspartate aminotransferase) which are found in blood. These are enzymes that are stored in liver cells and are released into the blood stream when those cells become inflamed. They do not identify what the cause of the damage is or whether it is ongoing or temporary. A series of high ALT and AST scores suggest, but do not prove, ongoing liver inflammation. These should be routinely monitored in people with HIV whether or not they have viral hepatitis.

A protein routinely tested for in people with hepatitis is alpha-feta protein (AFP or a-FP). This is because significant rises in it are associated with liver cancer. The levels also rise with pregnancy so it does not prove that the liver has a tumour and a substantial number of people with tumours do not have raised AFP levels but it can be used as a simple screening mechanism for tumours or the effectiveness of cancer treatments. Levels need to rise over 50 times the normal amount before they approach those seen in cancer and levels above the normal range but below cancerous levels are not unusual in chronic hepatitis.

A number of other enzymes and proteins are also routinely monitored to try and understand about the state of a person's liver. As with much of medicine the results of a number of tests are often needed and it is usually the combination of these results over a long period, possibly years, that decide what course of treatment should be recommended rather than a reliance on any single test on one occasion.

Liver biopsy: A long needle is inserted into the person and a sliver of the organ removed. There are a few different ways of grading the inflammation of the liver but a biopsy result should generally show if the liver has fibrosis, cirrhosis and the degree of damage. Fibrosis is the development of hard tissue in the liver as a result of inflammation but is reversible if the inflammation is reduced or prevented. Cirrhosis is a further stage when the liver has become so scarred that those cells can no longer function properly. This was believed to be a permanent loss of function by liver cells but on rare occasions some liver tissue appears to have recovered from cirrhosis although this is not well understood. This has also made the distinction between severe fibrosis and mild cirrhosis a little less clear. The liver is a large organ so that as parts become scarred other parts of the organ start to work harder to cope with the loss of function. However as more and more of the liver becomes inflamed, fibrotic and cirrhotic it becomes less and less able to cope with the demands placed upon it.

A non-invasive test that may be carried out is an ultra-sound scan (USS). A special camera is moved over the stomach and pictures taken of a person’s organs. These pictures are not high definition and are difficult for a lay person to follow or indeed make out what is on the screen often. They may be recommended for people with cirrhosis to check for the presence of tumours on a six monthly basis. Cirrhosis cannot be detected on an USS.