Diagnostic criteria for autoimmune hepatitis.

Diagnosis of Autoimmune Hepatitis (AIH) often represents a clinical challenge. The clinical spectrum of disease is quite heterogeneous. AIH can affect patients of all age groups, both sexes, and any race and region. The course may range from subclinical and very mild to acute attacks of hepatitis up to fulminant hepatic failure. Other patients present very late with the picture of cryptogenic cirrhosis. Laboratory features may also differ. Autoantibodies vary, and some patients do not display any autoantibodies at the time of clinical presentation. SLA/LP-autoantibodies are the only antibodies specific for the diagnosis of AIH, but they are only present in about 20% of cases. The most common feature in all patients with AIH is an elevation of IgG levels, usually a selective or highly preferential elevation of IgG in comparison to IgA and IgM. However, in some patients the relative increase in IgG levels may be within the normal limits, because the normal range is quite wide. The diagnosis of AIH should not be made without a liver biopsy showing inflammatory hepatitis. Histology mayshow typical features such as enrichment of plasma cells and piecemeal necroses, but distinction from other inflammatory liver disease including allergic drug reactions may be difficult. The International Autoimmune Hepatitis Group has tried to define diagnostic criteria on the basis of consensus discussions. These were revised in 1999 in the light of some clinical studies. However, the criteria are complicated, and not useful in everyday practise. In addition, the criteria were only designed as a scientific tool in order to create comparable groups in publication from different centres. Therefore, the International Autoimmune Hepatitis Group has re-approached the problem with the aim of defining simplified criteria for everyday use. With the help of various specialised centres in the world we evaluated a number of hypothetical criteria, and found out, that four criteria with two categories are sufficient to either make or exclude the diagnosis of AIH with positive and negative predictive values well over 90%: 1 point2 points1. IgG>16 g/l>18 g/l2. ANA, SMA>1 : 40>1 : 80 or SLA/LP+3. Histologycompatible withtypical for AIH4. Viral markersnegativeA value of 6 or more points makes the diagnosis of AIH very likely, a value of 7 or 8 points demonstrates definite AIH. The simplified criteria should help in the diagnosis of AIH in patients with liver disease, and they seem to be valid world-wide. Prospective data are needed to validate these criteria further.