Evaluating patients with chronic liver disease in whom the diagnosis of chronic active autoimmune hepatitis is suspected
Enzyme-Linked Immunosorbent Assay (ELISA)
Serum
Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 0.5 mL
0.4 mL
Gross hemolysis | OK |
Gross lipemia | OK |
Gross icterus | OK |
Heat treated specimens | Reject |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum | Refrigerated (preferred) | 21 days | |
Frozen | 21 days |
Evaluating patients with chronic liver disease in whom the diagnosis of chronic active autoimmune hepatitis is suspected
Negative: <20.0 U
Weak Positive: 20.0-30.0 U
Positive: >30.0 U
A negative result for anti-F-actin antibodies does not exclude a diagnosis of AIH.
In a study conducted at Mayo Clinic, the F-actin enzyme-linked immunosorbent assay (ELISA) had a clinical sensitivity of 92.9% when using the manufacturer's recommended cutoff of 20.0 U. In addition, the F-actin ELISA had a clinical specificity of 76.7% when using the aforementioned cutoffs. See Supportive Data.
Serologic tests for autoantibodies, including anti-filamentous-actin (F-actin), should not be relied upon exclusively to determine the etiology or prognosis of patients with liver disease.
A negative result for anti-F-actin antibodies does not exclude a diagnosis of autoimmune hepatitis (AIH).
In a study performed at Mayo Clinic, 173 serum samples submitted for clinical testing for anti-smooth muscle antibodies (anti-SMA), as performed by indirect immunofluorescence, were collected. These samples were subsequently tested using the anti-filamentous-actin (F-actin) antibody enzyme-linked immunosorbent assay (ELISA). By using the manufacturer's cut-offs for the 2 tests (negative at <20.0 units for the F-actin ELISA and <1:20 titer for the anti-SMA indirect immunofluorescence), the 2 tests had an overall concordance of 79.8%. In addition to the analytical concordance, patient histories were abstracted for diagnoses related to liver dysfunction. Of the 14 patients with autoimmune hepatitis, 13 were positive (> or =20.0 units) for F-actin antibodies by ELISA, which corresponded to a sensitivity of 92.9%. Of the remaining 159 patients who had a diagnosis of something other than autoimmune hepatitis, 122 were negative (<20.0 units), which corresponded to a specificity of 76.7%. In comparison, at a clinical specificity of 76.1%, which is similar to the ELISA, the anti-SMA indirect immunofluorescence method had a significantly lower clinical sensitivity of 78.6%. Positivity for either anti-F-actin antibodies or anti-SMA improved the diagnostic sensitivity to 92.9%, although the specificity decreased to 66.0%. This data indicates that the ELISA for F-actin antibodies may have improved diagnostic utility in comparison to the anti-SMA by indirect immunofluorescence, although a combination of these tests may be useful for some patients.
1. Mieli-Vergani G, Vergani D, Czaja AJ, et al: Autoimmune hepatitis. Nat Rev Dis Primers. 2018 Apr 12;4:18017
2. Terziroli Beretta-Piccoli B, Mieli-Vergani G, Vergani D: Serology in autoimmune hepatitis: A clinical-practice approach. Eur J Intern Med. 2018 Feb;48:35-43
3. Hennes EM, Zeniya M, Czaja AJ, et al: Simplified criteria for the diagnosis of autoimmune hepatitis. Hepatology. 2008 Jul;48(1):169-176
The method used to detect antibodies directed against filamentous-actin (F-actin) is enzyme-linked immunosorbent assay (ELISA). Prediluted controls and diluted patient sera are added to separate wells, allowing any actin antibodies present to bind to the antigen. Unbound sample is washed away, and an enzyme labeled anti-human IgG is added to each well. A second incubation allows the enzyme labeled anti-human IgG to bind to any patient antibodies, which have become attached to the microwells, and any unbound conjugate is removed by another wash step. The bound conjugate is visualized with 3,3',5,5' tetramethylbenzidine (TMB) substrate, which gives a blue reaction product, the intensity of which is proportional to a concentration of autoantibody in the sample. Sulfuric acid is added to each well to stop the reaction. This produces a yellow endpoint color, which is read at 450 nm. Testing is performed on the DS2 instrument by Dynex.(Package insert: QUANTA Lite Actin IgG ELISA 708785. INOVA Diagnostics; Rev. 5, 02/2015)
Monday
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
83516
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
FACT | F-Actin Ab, IgG, S | 44706-0 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
FACT | F-Actin Ab, IgG, S | 44706-0 |