Laboratory investigations - autoimmune liver disease investigations

Overview

A panel of autoantibodies distinguishes the three main autoimmune liver diseases, each with a characteristic serological signature alongside its own clinical/histological pattern
Autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis each show female predominance except PSC, which is more common in men and strongly linked to inflammatory bowel disease

Antibody	Condition
ASMA (anti-smooth muscle antibody)	Autoimmune hepatitis (type 1)
Anti-LKM1	Autoimmune hepatitis (type 2, typically younger patients)
AMA (anti-mitochondrial antibody)	Primary biliary cholangitis - present in ~95%
p-ANCA (atypical)	Can be positive in PSC and autoimmune hepatitis, less specific

AMA is highly sensitive and specific for PBC - a positive AMA with a cholestatic LFT pattern (raised ALP/GGT) is often sufficient for diagnosis without biopsy
ASMA/anti-LKM1 support but do not alone confirm autoimmune hepatitis - liver biopsy (interface hepatitis) remains important, and diagnosis uses a composite scoring system incorporating antibodies, IgG level, and histology
PSC is diagnosed primarily by imaging (MRCP) showing characteristic "beaded" bile duct strictures - autoantibodies are supportive but non-specific

Autoimmune hepatitis - corticosteroids +/- azathioprine (steroid-sparing)
PBC - ursodeoxycholic acid first-line
PSC - no proven disease-modifying medical therapy; managed with surveillance for cholangiocarcinoma/colorectal cancer (given the IBD association) and liver transplantation for end-stage disease

Inflammatory bowel disease (especially ulcerative colitis - PSC), Sjogren's syndrome and other autoimmune disease (PBC overlap), cholangiocarcinoma (PSC)

AMA-negative PBC exists (a small minority) and does not exclude the diagnosis if the clinical/biochemical/histological picture is otherwise typical

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