Rheumatoid Factor (Nephroplex) – Serum
This test measures the presence of rheumatoid factor, an antibody that may indicate an autoimmune response often linked to rheumatoid arthritis.
["Rheumatoid factor can help identify possible autoimmune conditions, though it’s not definitive on its own."]
Key facts at a glance
- LOINC
- 15205-8
- Short code
- Rheumatoid fact Ser Neph-aCnc
- Synonyms
- Rheumatoid fact Ser Neph-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- nephelometry
- 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 Is Rheumatoid Factor?
Rheumatoid factor (RF) is an antibody produced by the immune system in some people with autoimmune diseases, such as rheumatoid arthritis. It may also appear in other conditions or without symptoms. This test detects RF levels in your blood, specifically using a method called nephelometry, which measures light scattering for precise results.
Why Might You Need This Test?
Your doctor may order this test if you have symptoms like joint pain, swelling, or stiffness—common in rheumatoid arthritis—or if you have a family history of autoimmune diseases. It can also be part of a routine check for certain conditions or during monitoring of existing autoimmune disorders.
What Does a Positive Result Mean?
A positive rheumatoid factor result suggests an increased likelihood of an autoimmune response, but it doesn’t always mean you have rheumatoid arthritis. Other conditions or even normal aging can cause elevated levels. Your doctor will consider your symptoms, medical history, and other test results to make a diagnosis.
What Does a Negative Result Mean?
A negative rheumatoid factor result means your blood did not contain detectable levels of this antibody, but it doesn’t rule out autoimmune diseases entirely. Some people with rheumatoid arthritis have low or undetectable RF levels, so additional testing may be needed.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Rheumatoid factor is often used as a screening tool because it’s relatively easy and inexpensive to test. However, it’s not specific to rheumatoid arthritis—it can appear in other autoimmune diseases (like lupus or Sjogren’s syndrome) or in people without symptoms. Doctors may use it alongside other tests (like anti-CCP antibodies or imaging) to narrow down possible conditions. While it doesn’t diagnose arthritis alone, it can signal a need for further evaluation.
Short name
Rheumatoid Factor (Neph)
Frequently asked questions
How is this test performed?
What kind of specimen is used?
Can results change over time?
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