Introduction

Appropriate biomarkers are needed to detect hepatic disease, to direct diagnostic work-up, to estimate disease severity, to assess prognosis and to evaluate therapy. The available tests can be divided into essential and special static tests and dynamic tests. On the one hand the traditional static tests are only an indirect measure of hepatic function or damage, and these tests involve the measurement of endogenous substances at a single point in time. Dynamic tests, on the other hand, reflect real-time hepatic function. In these tests, the dimension of time is also considered. The clearance of a test substance or the formation rate of a metabolite reflects the actual performance of the liver.

Static tests

The essential static tests for hepatobiliary disease are summarized in Table 15.1. The pattern of these conventional tests indicates which more specialist tests are likely to be valuable. There are several limitations associated with these conventional liver function tests. Test results of liver enzymes and clotting factors can be affected by the substitution of blood components. Falling aminotransferase values are only reassuring when accompanied by a restoration of metabolic function. Aminotransferases, alkaline phosphatase and bilirubin lack organ specificity. The long plasma half-life of cholinesterase does not allow the detection of rapid changes in hepatic function. Most importantly, the conventional tests are only of limited prognostic value.