F-Actin (Smooth Muscle) Antibody, IgG with Reflex to IgG Titer

Label Mnemonic:	ACTIN
Epic code:	LAB8686
Order form:	Epic Req
Downtime form:	Doctor/Provider Orders - Pathology Core and Specialty Care Nursery

Commercial Mailout Laboratory
6240-8 RCP
356-8593

Specimen(s):

Serum

Collection Medium:

Red top tube 5 mL (Clot Activator)

Minimum:

Preferred Minimum: 0.5 mL serum
Absolute Minimum: 0.4 mL serum

Rejection Criteria:

Plasma. Contaminated, heat-inactivated, hemolyzed, or lipemic specimens.

Turn Around Time:

2 – 8 days upon receipt at reference laboratory

Reference Range:

Negative: <20.0 U

Weak Positive: 20.0-30.0 U

Positive: >30.0 U

Interpretive Data:

Positivity for anti-filamentous-actin (F-actin) antibodies may help support a diagnosis of autoimmune hepatitis (AIH) following exclusion of other causes of hepatitis.

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.

Comments:

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.

Methodology:

Enzyme-Linked Immunosorbent Assay (ELISA)

CPT Code:

83516