Description

1. Purpose: The test is used to aid in the diagnosis of autoimmune liver diseases, particularly autoimmune hepatitis (AIH). It helps differentiate AIH from other liver diseases and assess the severity of the autoimmune response.
2. Methodology: The test utilizes an indirect immunofluorescence assay (IFA) technique. In this assay, patient serum is incubated with tissue sections of liver or kidney that contain microsomes (cellular organelles). If LKM antibodies are present in the serum, they bind to the microsomes in the tissue sections. After washing away unbound antibodies, a fluorescent-labeled secondary antibody is applied. Under a fluorescence microscope, the presence of fluorescence indicates the presence of LKM antibodies.
3. Target Antigen: The target antigens for LKM antibodies are cytochrome P450 enzymes, particularly CYP2D6, found in the liver microsomes. These antibodies may also react with similar enzymes present in the kidney microsomes, hence the name “Liver Kidney Microsomal” antibodies.
4. Clinical Utility: The presence of LKM antibodies is strongly associated with autoimmune hepatitis (AIH), particularly Type 2 AIH. However, LKM antibodies may also be found in a subset of patients with Type 1 AIH or other autoimmune liver diseases. The test results, along with clinical and other laboratory findings, aid in the diagnosis and classification of AIH.
5. Interpretation: The test results are reported as positive or negative based on the presence or absence of fluorescent staining. Titers of LKM antibodies may also be reported, indicating the concentration of antibodies in the serum. Higher titers are generally associated with more severe autoimmune liver disease.
6. Limitations: While the presence of LKM antibodies is strongly associated with autoimmune liver diseases, including AIH, it is not specific to AIH and may be found in other conditions. Additionally, some medications and environmental factors may induce the production of LKM antibodies, leading to false-positive results.

Overall, the Liver Kidney Microsomal (LKM) Antibody, IFA test is a valuable tool in the diagnosis and management of autoimmune liver diseases, particularly autoimmune hepatitis. It provides valuable information that helps guide treatment decisions and monitor disease progression.