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Test ID: STR    
Striational (Striated Muscle) Antibodies, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

This test is a useful serological aid in the diagnosis of thymoma, especially in patients with onset of myasthenia gravis (MG) younger than 45 years.

 

It is more predictive of thymoma when accompanied by a muscle acetylcholine receptor (AChR) modulating antibody value of > or =90% AChR loss and is most predictive of thymoma when accompanied by CRMP-5-IgG.

 

It is useful as a screening test for MG in older patients, especially when tests for muscle AChR antibodies are negative.

 

Serial measurements are useful in monitoring the efficacy of immunosuppressant treatment in patients with MG.

 

Serial measurements are useful after treatment of thymoma. Measurements of muscle AChR binding, muscle AChR modulating antibody, and CRMP-5-IgG (if initially positive) are also recommended.

 

Serial measurements in recipients of D-penicillamine or bone marrow allografts may be useful in monitoring autoimmune complications and graft-versus-host disease, respectively.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Autoantibodies directed against the contractile elements of striated muscle are found in 30% of adult patients with myasthenia gravis and in 80% of those with thymoma. These antibodies may also be detected in patients with: Lambert-Eaton myasthenic syndrome, small-cell lung carcinoma, breast carcinoma, patients treated with D-penicillamine, bone marrow transplant recipients having graft-versus-host disease, and autoimmune liver disorders.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

<1:60

Interpretation Provides information to assist in interpretation of the test results

Autoantibodies reactive with contractile elements of skeletal muscle are detectable in sera of approximately 30% of patients with acquired (autoimmune) myasthenia gravis (MG) and 74% of patients with thymoma in association with MG.

 

Striational antibodies occur also in approximately:

-14% of patients with thymoma without clinical evidence of MG

-25% of rheumatoid arthritis (RA) patients treated with D-penicillamine, 4% in untreated RA patients

-5% of patients with Lambert-Eaton myasthenic syndrome (LES) and/or small-cell lung carcinoma (SCLC) (MGLES / Myasthenia Gravis [MG]/Lambert-Eaton Syndrome [LES] Evaluation and PAVAL / Paraneoplastic Autoantibody Evaluation, Serum)

-In some bone marrow recipients with graft-versus-host disease

 

The incidence in healthy subjects is <1%.  

 

A rising titer after removal of thymoma may be indicative of tumor recurrence.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

A negative result does not exclude the presence of thymoma (20% are negative).

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Cikes N, Momoi MY, Williams CL, et al: Striational autoantibodies: quantitative detection by enzyme immunoassay in myasthenia gravis, thymoma, and recipients of D-penicillamine or allogeneic bone marrow. Mayo Clin Proc 1988 May;63(5):474-481

2. Lennon VA: Serological profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome. Neurology 1997;48(Suppl 5):S23-S27

3. Vernino S, Lennon VA: Muscle and neuronal autoantibody markers of thymoma: neurological correlations. Ann NY Acad Sci 2003 Sep;998:359-361

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test