Over 100 types of liver disease exist!

The liver is the largest gland and largest organ in the body. It plays an important part in intermediary metabolism via a vast range of functions. The liver fights infections and disease, detoxifies the body, filters and cleans the blood, produces hormones, enzymes and proteins and repairs damage. Disease of the liver may be caused by infection, exposure to toxic products, injury, or genetic defects. There is over 100 types of liver disease for example hepatitis, cirrhosis, fatty liver disease and cancer.

Accordingly, liver function tests should be interpreted with care. For example, the liver produces approximately 300 mg of bilirubin daily but a healthy liver can metabolise and excrete approximately 10 times this amount. As a result of this functional reserve, bilirubin is an insensitive test of liver function. Specificity is also an issue, as raised bilirubin levels may occur at different stages throughout the process.  

Negative results are also valuable as they indicate a low probability of significant disease. It is important to recognise that the standard liver function test profile offers limited quantitative information and measures dysfunction or damage rather than function. The liver has only a limited number of responses to various pathological insults. Signs, symptoms and management problems in patients with hepatic disease often relate more to liver pathology than to aetiology of the condition. From an aetiological point of view, the standard liver function test profile is not particularly helpful but may be able to categorise the patient as hepatocellular, cholestatic, chronic hepatitis, cirrhotic, etc.. Despite this, the simplicity and low cost of the standard liver function test profile has meant that it constitutes a significant proportion of the workload of a typical laboratory. In primary care, abnormal results for liver function may not be adequately investigated, missing an important chance of identifying treatable chronic liver disease.

Liver function tests can be used to answer 3 questions:

• Is liver disease present?
• What is the nature