Test Catalog

Test Id : RNAP

RNA Polymerase III Antibodies, IgG, Serum

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

Evaluating patients suspected of having systemic sclerosis as part of systemic sclerosis criteria antibody tests


Providing diagnostic and prognostic information in patients with systemic sclerosis

Method Name
A short description of the method used to perform the test

Enzyme-Linked Immunosorbent Assay (ELISA)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

RNA Polymerase III Ab, IgG, S

Lists additional common names for a test, as an aid in searching

RNA Polymerase III Ab, IgG, S

Specimen Type
Describes the specimen type validated for testing


Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.4 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus OK
Heat-treated Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 21 days
Frozen 21 days

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

Evaluating patients suspected of having systemic sclerosis as part of systemic sclerosis criteria antibody tests


Providing diagnostic and prognostic information in patients with systemic sclerosis

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

Systemic sclerosis (SSc) is a multisystem autoimmune connective tissue disease characterized by vascular dysfunction, fibrotic changes in the skin and internal organs as well as an autoimmune response manifested by production of diverse antibodies.(1,2) While the clinical manifestations and severity of SSc are highly variable, two main subsets are widely recognized. These include the limited cutaneous SSc (lcSSc) and diffuse cutaneous SSc (dcSSc) subtypes of which the diffuse form has the worse prognosis and survival rates.(2) Immunologically, SSc is characterized by the presence of several disease-specific and mutually exclusive autoantibodies considered helpful in the diagnosis, stratification, and prognosis of disease.(1-3) Of the described autoantibodies, the 2013 American College of Rheumatology/European League against Rheumatism classification criteria for SSc recommends testing for centromere, topoisomerase I (topo I or Scl 70), and RNA polymerase III autoantibodies.(3) Antibodies to Scl 70 and RNA polymerase III are generally associated with dcSSc while those to centromere typically correlate with the lcSSc form of disease.(1-3)


The human nuclei consist of three RNA polymerases, RNA polymerase I, II and III.(4) Of these, antibodies targeting RNA polymerases I and III are always present together and are most common in patients with SSc. The RPC155 immunodominant epitope has been identified in autoantibodies associated with anti-RNA polymerase I/III in patients with SSc and is widely used in solid-phase immunoassays for the detection and quantification of anti-RNA polymerase III antibodies in clinical laboratories.(5)


The prevalence of anti-RNA polymerase III antibodies in patients with SSc is variable with a pooled prevalence of 11% and ranges from 0 to 41% in different studies.(4) This variability may be due to environmental and genetic factors as well as lack of harmonization of immunoassays for the detection of antibodies.(4,6) Positivity for anti-RNA polymerase III antibody is generally mutually exclusive of other SSc-specific antibodies such as centromere and Scl 70.(1-3) In addition, SSc patients who test positive for anti-RNA polymerase III antibody have increased risk for the diffuse cutaneous involvement, hypertensive kidney disease, and poor prognosis.(1,2)

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.

<20.0 U (negative)

20.0-39.9 U (weak positive)

40.0-80.0 U (moderate positive)

>80.0 U (strong positive)

Provides information to assist in interpretation of the test results

A positive result for RNA polymerase III antibody may support a diagnosis of systemic sclerosis (SSc) in the appropriate clinical context (see Cautions). Anti-RNA polymerase III autoantibody in patients with SSc is associated with the diffuse cutaneous form of disease and an increased risk of sclerodermal renal crisis. 


A negative result indicates no detectable IgG antibodies to RNA polymerase III and does not rule out a diagnosis. The RNA polymerase III IgG ELISA tests only for the RP155 dominant epitope, other epitopes in the antigenic complex are absent and cannot be detected.(6) The overall pooled prevalence of anti-RNAP polymerase III antibody is reported to be 11%, 95% confidence interval: 8 to 14, range of 0 to 41% in published studies.(4)

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

A positive result indicates detectable anti-RNA polymerase III above assay cutoff and does not unequivocally establish a diagnosis of systemic sclerosis.(6,7)


Enzyme immunoassay to detect anti-RNA polymerase III antibody uses an immunodominant epitope as antigen. Negative result does not also rule out the presence of antibodies targeting other epitopes in the RNA polymerase I/III antigens.


The level of RNA polymerase III autoantibodies does not indicate the severity of disease in patients with systemic sclerosis (SSc). However, patients with high positive anti-RNA polymerase III antibody titers are more likely to have SSc compared to those with low antibodies.(7)


Anti-RNA polymerase III antibodies may occur prior to clinical onset of SSc.(7)


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.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Stochmal A, Czuwara J, Trojanowska M, Rudnicka L: Antinuclear antibodies in systemic sclerosis: An update. Clin Rev Allergy Immunol. 2020 Feb;58(1):40-51

2. Nihtyanova SI, Sari A, Harvey JC, et al: Using autoantibodies and cutaneous subset to develop outcome-based disease classification in systemic sclerosis. Arthritis Rheumatol. 2020 Mar;72(3):465-476

3. van den Hoogen F, Khanna D, Fransen J, et al: 2013 classification criteria for systemic sclerosis: an American College of Rheumatology/European League against Rheumatism collaborative initiative. Arthritis Rheum. Arthritis Rheum. 2013 Nov;65(11):2737-2747. doi: 10.1002/art.38098

4.Sobanski V, Dauchet L, Lefevre G, et al: Prevalence of anti-RNA polymerase III antibodies in systemic sclerosis: New data from a French cohort and a systematic review and meta-analysis. Arthritis Rheumatol. 2014 Feb;66(2):407-417. doi: 10.1002/art.38219

5. Kuwana M, Kimura K, Kawakami Y: Identification of an immunodominant epitope on RNA polymerase III recognized by systemic sclerosis sera: application to enzyme-linked immunosorbent assay. Arthritis Rheum. 2002 Oct;46(10):2742-2747

6. Damoiseaux J, Potjewijd J, Smeets RL, Bonroy C: Autoantibodies in the disease criteria for systemic sclerosis: The need for specification for optimal application. J Transl Autoimmun. 2022 Jan 4;5:100141. doi:10.1016/j.jtauto.202

7. Burbelo PD, Gordon SM, Waldman M, et al: Autoantibodies are present before the clinical diagnosis of systemic sclerosis. PLoS One. 2019 Mar 26;14(3);e0214202

Method Description
Describes how the test is performed and provides a method-specific reference

The immunodominant fragment of RNA polymerase III antigen is derived from recombinant DNA technology. Purified RNA polymerase III antigen is adsorbed to the wells of a polystyrene microtiter plate under conditions that preserve the antigen in its antigenic state. Prediluted controls and diluted patient sera are added to separate wells. Unbound sample is washed away, and an enzyme-labeled antihuman IgG conjugate is added to each well. After incubation and washing away of unbound enzyme-labeled antihuman IgG, the bound conjugate is measured by adding a chromogenic substrate. The intensity of the absorbance produced is measured with an automated microwell plate reader. Results are calculated by comparison to a single-point calibrator.(Package insert: QUANTA Lite RNA Pol III. INOVA Diagnostics; 02/2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Tuesday, Thursday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 7 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

14 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
RNAP RNA Polymerase III Ab, IgG, S 79182-2
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.
RNAP RNA Polymerase III Ab, IgG, S 79182-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports