RNA Polymerase III

Category: Rheumatology
Test Code: 063
Disease: Scleroderma
Methodology: ELISA
Reference Range: Negative <20; Weak Positive 20-39; Moderate Positive 40-80; Strong Positive >80
Units: Units/ml
CPT Code: 83520
Schedule / Turnaround Time: Assay performed once per week. Report availability is within one week from the time of specimen receipt.
Specimen Requirements:

Specimen need not be refrigerated or frozen. Collect 2-3 ml of blood in a red top or serum separator tube. If possible, separate serum from clot and place into white tube provided with Immco Diagnostics’ collection kits. If separation facilities are not available, the blood can be sent in the tube used for collection.

Sample Stability:

Sample is stable at ambient temperature during shipment. If sample is stored prior to shipment, it is stable refrigerated (2-8˚C) up to five days and frozen (-20˚C or lower) up to one year.


Autoantibodies to RNA Polymerase III antigen are found in 11% to 23% of patients with systemic sclerosis. Patients who are positive for RNA Polymerase III antibodies do not have any of the other antibodies typically found in systemic sclerosis patients such as centromere, Scl-70, or Pm/Scl antibodies. Thus, they are a separate serologic group. Numerous studies have shown that these patients have an increased risk of the diffuse cutaneous form of scleroderma, with high likelihood of skin involvement and hypertensive renal disease. Antibodies to several different types of RNA Polymerases are found in patients with systemic sclerosis. The recombinant immunodominant epitope of RNA Polymerase III can be used in ELISA with high specificity to detect RNA Polymerase III antibodies in patients with the diffuse cutaneous form of systemic sclerosis.