At its onset, acute hepatitis mimics various non-specific diseases. Usually, hepatitis is suspected only when jaundice develops. At this stage hepatitis should be differentiated from other disorders associated with jaundice.
Hepatitis diagnosis includes non-specific liver function tests: aminotransferases (ALT and AST), bilirubin, alkaline phosfatase, etc. AST and ALT are usually highly elevated in hepatitis (> 400 IU/L) and ALT is usually higher than AST. The level of aminotransferases not always correlates with clinical severity of hepatitis, which means that ALT and AST can be markedly increased, but the evolution of hepatitis can be relatively mild, and vice versa.
Hyperbilirubinemia can be variable in hepatitis and usually is preceded by urinary bilirubin (darkening of urine). Alkaline phosphatase is moderately elevated in hepatitis.
If viral hepatitis is suspected, it is necessary to effectuate serological studies, to determine the type of virus.