Measuring blood levels of the enzyme, serum alanine aminotransferase (ALT), is the most common way to test for liver disease.
Blood enzyme levels above a certain value indicate liver disease.
A new study recommends lowering the current upper limit of normal blood ALT levels.
Researchers suspected that the studies that set the currently accepted normal levels included patients with liver disease that could not be detected when the studies were done.
They studied 6835 first-time blood donors who tested negative for hepatitis C virus (HCV).
| Studies that set accepted normal ALT levels included patients with undetected liver disease.
| Annals of Internal Medicine |
The researchers defined the "normal" level of ALT as the mean value of ALT levels of those at lowest risk for liver disease.
They found a substantially lower value for the upper end of the range of normal ALT than laboratories currently use.
They recommend using the new, lower level to define ALT levels that would indicate liver disease.
An editorial says that the study "was carefully done and the results unquestionably correct".
However, using the new normal limits for ALT to decide who has liver disease would cause many millions of patients to be identified with "abnormal" ALT levels.
Evaluating these people for liver disease could "overwhelm the health care system," the writer says.
Most of these people would be found to have liver diseases that are not serious and seldom progress to serious liver disease.