Liver-function tests are part of the routine blood screen used to try to make a specific diagnosis when the symptoms are vague. Abnormality in these tests is sometimes a pointer to more detailed tests. Two common causes of abnormal liver function are excess alcohol and viral infections that cause the liver to become inflamed. If too much alcohol is the cause, the tests may return to normal within a couple of months. If the liver has been permanently damaged by alcohol, the tests may not return to normal even if you stop drinking. Viral infections, such as hepatitis B and C and glandular fever can also cause abnormal liver function.

Is it possible to have a paternity test done without going through a solicitor or the Child Support Agency? I want to discover who is the father of my son.

Paternity tests based on DNA technology are very accurate and can be done on a tiny sample of blood. It is essential to have a sample from both the child and the presumed father. Commercial laboratories will perform these tests, and you need not involve the CSA of a solicitor. The Department of Health has published a code of practice for labs. The biggest lab providing this service is Cellmark Diagnostics (01235 528 000).

Please send your questions to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax 020-7005 2182, or e-mail to Dr Kavalier regrets that he is unable to respond personally to questions