Italian Society of Clinical Pathology and Laboratory Medicine (SIPMeL) guidelines on the use of autoantibody tests in the diagnosis of autoimmune liver diseases.

Autoimmune liver diseases (AILDs) are considered rare conditions, though the frequency of their diagnosis is increasing thanks to the introduction of new diagnostic tests and improvements in analytical technologies. In clinical practice, in patients with liver disease of unknown etiology, after a differential diagnosis that excludes other possible causes of hepatic damage, a potential autoimmune origin should be investigated through the evaluation of a specific autoantibody panel. In this context, the diagnostic laboratory plays a pivotal role, since the detection of well-defined autoantibody patterns is essential in the diagnosis and classification of autoimmune liver disorders. In 2009, the Study Group on Autoimmunology (GdS-AI) of the Italian Society of Clinical Pathology and Laboratory Medicine (SIPMeL) issued recommendations pertaining to a rational approach to the interpretation and clinical application of autoantibody testing in autoimmune hepatitis and cholestatic diseases. Then, after fourteen years, the GdS-AI deemed it necessary to revise and update the recommendations for the use of autoantibody testing in the diagnosis and monitoring of AILDs. This updated document provides a summary of the current analytical methodologies and autoantibody markers available for the diagnosis and monitoring of autoimmune liver disorders, together with recommendations regarding the appropriate use of tests and the interpretation of results. The guidelines were prepared after a systematic review of the most recent scientific literature and are structured into 19 specific recommendations, subdivided by disease type into autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC). The quality of evidence and strength of each recommendation were assessed following the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach, ensuring a rigorous and transparent methodology aimed at producing efficient and clinically effective diagnostic recommendations. These guidelines are designed to support laboratory professionals and clinicians in the selection, application, interpretation, and reporting of autoantibody testing in AILDs, improving diagnostic accuracy and clinical outcomes through evidence-based laboratory medicine.