When lab tests show that the liver does not function properly for a long period of time, they do not necessarily mean that there is liver damage -- rather, the tests might suggest damage in the muscle. This information is important for the early diagnosis of muscle diseases and the prevention of unnecessary and invasive liver biopsies.
When the liver enzyme count is higher than the normal, the first thing to check is whether the patient suffers from a liver disease. Some of the standard tests most of us take from time to time include ALT (Alanine Transaminase, also known as SGPT) and AST (Aspartate Transaminase, also know as SGOT) levels, which check liver functioning. However, sometimes the results suggest muscle damage, and not a liver damage; results that might suggest that will show that while the AST and ALT levels are abnormal, the GPT (Glutamic-Pyruvic Transaminase) level is normal.
It is important to check whether there is muscle damage when the liver function is high, and there is no clear evidence of a liver disease. In such cases, the levels of muscle's enzymes such as CPK (Creatine Phosphokinase) should be checked. If the CPK level is very high (>1000), the liver dysfunction is probably caused by a muscle disease.
This tip courtesy of Prof. Yoram Nevo, Neuropediatric Unit, Mount Scopus Hospital.