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HelpTest ID RNAP RNA Polymerase III Antibodies, IgG, Serum
Useful For
Evaluating patients suspected of having systemic sclerosis, when used in conjunction with centromere and Scl70 antibodies
Providing diagnostic and prognostic information in patients with systemic sclerosis
Method Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Reporting Name
RNA Polymerase III Ab, IgG, SSpecimen Type
SerumContainer/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 0.5 mL
Forms: If not ordering electronically, complete, print, and send a Neurology Test Request Form-General (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)
Specimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 21 days |
| Frozen | 21 days |
Clinical Information
Systemic sclerosis is a multisystem connective tissue (systemic rheumatic) disease characterized by fibroblast dysfunction leading to fibrosis of the skin and internal organs, microvascular injury leading to tissue hypoxia, and an autoimmune response manifested by production of autoantibodies.(1,2) The severity of the disease is highly variable among individual patients. Limited cutaneous systemic sclerosis and diffuse cutaneous systemic sclerosis have been recognized as distinct subsets, with worse survival for those with the diffuse form.(2) Clinical features of CREST syndrome (calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasias) can be seen in both limited cutaneous and diffuse cutaneous forms but, overall, are associated with a better prognosis.(2) Several disease-specific and mutually exclusive autoantibodies have been identified that are helpful in both diagnosis and disease classification. Centromere and topoisomerase I (Scl 70) autoantibodies are associated with limited cutaneous systemic sclerosis and diffuse cutaneous systemic sclerosis, respectively.(3)
RNA polymerase III is a complex, 16-subunit enzyme directing transcription of small, stable nontranslated RNA genes: tRNAs, 5S rRNA, Alu-RNA and U6 7SK snRNA genes. The immunodominant epitope for autoantibodies with anti-RNA polymerase I/III specificity has been identified on the RNA polymerase-specific subunit RPC155.(4)
Autoantibodies to RNA polymerase III antigen are found in 11% to 23% of patients with systemic sclerosis.(1,4) Systemic sclerosis patients who are positive for RNA polymerase III antibodies form a distinct serologic subgroup and usually do not have any of the other antibodies typically found in systemic sclerosis patients such as anticentromere or anti-Scl70.(1) Numerous studies have shown that systemic sclerosis patients with anti-RNA polymerase III have an increased risk of the diffuse cutaneous form of scleroderma, with a high likelihood of skin involvement and hypertensive renal disease.(1,4)
Reference Values
<20.0 U (negative)
20.0-39.9 U (weak positive)
40.0-80.0 U (moderate positive)
>80.0 U (strong positive)
Cautions
A positive result indicates the presence of measurable IgG antibodies to RNA polymerase III, but does not unequivocally establish the diagnosis of systemic sclerosis or other autoimmune disease.
The level of RNA polymerase III autoantibodies does not indicate the severity of disease in patients with systemic sclerosis.
The presence of immune complexes or other immunoglobulin aggregates in the patient specimen may cause an increased level of nonspecific binding and produce false-positive results with this assay.
Day(s) Performed
Wednesday; Evening
Report Available
1 dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test has been cleared or approved by the U.S. 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.CPT Code Information
83520