RNA Polymerase III Antibody, Serum, Qualitative, Line Blot
This test looks for antibodies against RNA polymerase III in a blood (serum) sample. These antibodies are mainly used as a marker to help diagnose and monitor systemic sclerosis (scleroderma), especially the diffuse form.
["A positive RNA polymerase III antibody result supports a diagnosis of systemic sclerosis and may be linked to more widespread skin and internal organ involvement."]
Key facts at a glance
- LOINC
- 81737-9
- Short code
- RNAp III RP11 Ab Ser Ql Line blot
- Synonyms
- RNAp III RP11 Ab Ser Ql Line blot
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- line-blot
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
The test detects antibodies that your immune system may have made against RNA polymerase III, a protein complex your cells use to make certain types of RNA. Finding these antibodies in serum is a laboratory clue that your immune system is targeting your own tissues, which happens in some autoimmune diseases.
How the Sample Is Collected
A healthcare professional draws a small amount of blood from a vein, usually in your arm, into a tube. The serum (the clear liquid part of the blood) is separated and tested using a line blot method, which checks whether your sample reacts with specific antibody targets.
Why Your Doctor Ordered It
Doctors order this test when they suspect systemic sclerosis (scleroderma), particularly when skin tightening is widespread. It can help classify the type of scleroderma and estimate the chance of certain organ problems such as lung or kidney involvement, which guides monitoring and treatment.
What the Results Mean
A positive result means RNA polymerase III antibodies were detected and supports a diagnosis of systemic sclerosis; it is often associated with the diffuse form. A negative result means they were not detected, but it does not by itself rule out disease. Results are interpreted alongside your symptoms, exam findings, and other tests, and exact cutoffs vary by laboratory.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
RNA polymerase III antibodies are relatively specific for systemic sclerosis and are most often seen in the diffuse cutaneous subtype. They have been associated with a higher risk of rapidly progressive skin thickening and serious complications such as renal crisis, and with certain patterns of lung involvement. Because these antibodies are not present in everyone with scleroderma, a negative result does not exclude the disease, and results should always be interpreted by a clinician in the full context of the patient's presentation.
Short name
RNA Pol III Ab
Frequently asked questions
Does a positive result mean I definitely have scleroderma?
Can the antibody test be negative even if I have scleroderma?
Will I need this test repeated?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy