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HelpTest Code LAB1230211 Filamentous-Actin (F-actin) Antibody, IgG, Serum
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Reporting Name
F-Actin Ab, IgG, SSpecimen 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 Serum
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
| Heat treated specimens | Reject |
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 21 days |
| Frozen | 21 days |
Specimen Minimum Volume
Serum: 0.4 mL
Special Instructions
Day(s) Performed
Monday
Specimen Retention Time
14 daysReport Available
2 to 8 daysReference Values
Negative: <20.0 U
Weak Positive: 20.0-30.0 U
Positive: >30.0 U
Useful For
Evaluation of patients with hepatitis of unknown origin associated with hypergammaglobulinemia and/or abnormal liver enzymes
This test may also be useful for confirming positivity for smooth muscle antibodies.
Testing Algorithm
For more information First-Line Screening for Autoimmune Liver Disease Algorithm.
CPT Code Information
83516
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| FACT | F-Actin Ab, IgG, S | 44706-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| FACT | F-Actin Ab, IgG, S | 44706-0 |
Supportive Data
In a study performed at Mayo Clinic, 173 serum samples submitted for clinical testing for anti-smooth muscle IgG antibodies (anti-SMA) performed by indirect immunofluorescence assay (IFA) were collected. These samples were subsequently tested using the anti-filamentous-actin (F-actin) IgG antibody enzyme-linked immunosorbent assay (ELISA). 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(IFA), 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 (AIH), 13 were positive (≥20.0 units) for F-actin antibodies by ELISA, which corresponded to a sensitivity of 92.9%. Of the remaining 159 patients who had diagnoses other than AIH, 122 were negative (<20.0 units), which corresponded to a specificity of 76.7%. The anti-SMA IFA had a significantly lower clinical sensitivity of 78.6% than the F-actin ELISA with comparable specificity (76.1%). Positivity for either anti-F-actin antibodies or anti-SMA improved the diagnostic sensitivity to 92.9%, although with a decreased specificity of 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.