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HelpTest Code LKM Liver/Kidney Microsome Type 1 Antibodies, Serum
Reporting Name
Liver/Kidney Microsome Type 1 Ab, SUseful For
Evaluation of patients with liver disease of unknown etiology
Evaluation of patients with suspected autoimmune hepatitis
Testing Algorithm
For more information see First-Line Screening for Autoimmune Liver Disease Algorithm.
Method Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumSpecimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 21 days | |
| Frozen | 21 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | OK |
| Heat treated | Reject |
Special Instructions
Reference Values
≤20.0 Units (Negative)
20.1-24.9 Units (Equivocal)
≥25.0 Units (Positive)
Reference values apply to all ages.
Day(s) Performed
Monday, Wednesday, Friday
CPT Code Information
86376
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| LKM | Liver/Kidney Microsome Type 1 Ab, S | 32220-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| LKM | Liver/Kidney Microsome Type 1 Ab, S | 32220-6 |
Clinical Information
Autoimmune hepatitis (AIH) is chronic liver disease that results from a loss of immune system tolerance and recognition of self-antigens.(1) AIH occurs in children and adults, with a significant female predominance. The clinical presentation of AIH varies significantly from asymptomatic liver dysfunction to acute liver failure. Evidence of liver dysfunction manifests as elevated aspartate aminotransferase, alanine aminotransferase, and gamma glutaryl transferase in the context of normal alkaline phosphatase. In addition, most individuals with AIH display increased concentrations of total IgG.
AIH is associated with the production of diverse autoantibodies which also serves to subcategorize patients.(2) AIH type 1 is associated with F-actin reactive smooth muscle autoantibody (SMA), antinuclear autoantibody (ANA) (60% of patients), and autoantibody to SLA/LP (15% to 20% of patients), while AIH type 2 is associated with LKM-1 and LC-1 autoantibodies.(3) AIH type I occurs in children and adults and usually has a relatively mild course that is responsive to steroids and azathioprine. In contrast, AIH type 2 occurs predominantly in children, with a more moderate/severe disease course.
Most of the autoantibodies associated with AIH were originally detected and characterized by indirect immunofluorescence (IIF).(4) Anti-LKM-1 antibodies can be detected by IIF using rodent stomach/liver/kidney composite tissue; anti-LKM-1 antibodies display staining of the proximal tubules in the kidney and cytoplasmic staining of the hepatocytes, with no reactivity on the stomach tissue. The major target for anti-LKM-1 antibodies is the cytochrome P450 2D6 (CYP2D6).(5) Following the identification of this autoantibody target, a number of solid-phase immunoassays have been developed for the evaluation of anti-LKM-1 antibodies.
Although not diagnostic in isolation, the presence of certain autoantibodies has been reported to be important in establishing the diagnosis of AIH. Published diagnostic criteria for AIH which include testing for autoantibodies (ANA, SMA, anti-LKM-1, and anti-SLA), determination of serum immunoglobulin, histopathology, evaluation for viral hepatitis, and other indices have been developed based on scoring systems.(6-8). These diagnostic scoring systems are useful in AIH research studies and may not substitute appropriate clinical assessment in routine patient evaluation.
Interpretation
Seropositivity for anti-liver/kidney microsomal antibodies type 1 antibodies is consistent with a diagnosis of autoimmune hepatitis type 2, in patients with compatible clinical symptoms and histopathology.
Cautions
Serologic tests for autoantibodies, including anti-liver/kidney microsomal antibodies type 1 (anti-LKM-1), should not be relied upon exclusively to determine the etiology or prognosis of patients with liver disease.
Anti-LKM-1 antibodies are not the only serological marker for autoimmune hepatitis (AIH) and should be evaluated in the context of other AIH-associated autoantibodies, including antinuclear antibodies and smooth muscle antibodies.
Anti-LKM-1 antibodies may occur in some patients with chronic hepatitis caused by hepatitis C virus (HCV) infection. Although the epitopes recognized by anti-LKM-1 antibodies in HCV infection are different than in patients with AIH type 2, physicians must use caution in interpreting the results of tests for anti-LKM-1 antibodies in such patients.
Method Description
Purified full-length recombinant human cytochrome P450 2D6 antigen is bound to the wells of a polystyrene microwell plate under conditions that will preserve the antigen in its native state. Pre-diluted controls and diluted patient sera are added to separate wells, allowing any liver/kidney microsomal antibodies type 1 present to bind to the immobilized antigen. Unbound sample is washed away, and an enzyme labeled anti-human IgG antibody (conjugate) is added to each well. A second incubation allows the enzyme labeled anti-human IgG antibody to bind any patient antibodies, which have become attached to the microwells. After washing away any unbound enzyme labeled anti-human IgG antibody, the remaining enzyme activity is measured by adding a chromogenic substrate and measuring the intensity of the color that develops. The assay is evaluated by spectrophotometrically measuring and comparing the color intensity that develops in the patient wells with the color in the calibrator wells. (Package insert: INOVA Diagnostics, Inc.; Revision 13; 10/2018)