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Rheumatoid Factor (Neph) - Serum

Published: August 9, 2026Updated: August 17, 2026

This test measures the presence of rheumatoid factor, an antibody found in some people with rheumatoid arthritis or other autoimmune conditions.

Quick summary

["RF helps doctors assess possible autoimmune diseases like rheumatoid arthritis."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
15204-1
Short code
Rheumatoid fact Titr Ser Neph
Synonyms
Rheumatoid fact Titr Ser Neph
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
7.35
Ref high
7.45
Critical range
7.2 N/A – 7.6 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

Why This Test Is Done

Your doctor may order this test to help diagnose or monitor rheumatoid arthritis, lupus, or other autoimmune disorders. It can also be used to track disease activity or response to treatment. RF is not definitive for rheumatoid arthritis alone but can be part of a broader evaluation.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. The test is quick and typically done in a doctor’s office or lab.

What the Results Mean

Results are qualitative (positive or negative) and do not have a standard numeric range. A positive result suggests higher-than-normal levels of rheumatoid factor, which may indicate an autoimmune condition. False positives can occur, so results are often interpreted alongside other tests and symptoms.

Possible Conditions Linked to Positive Results

A positive rheumatoid factor test is most commonly associated with rheumatoid arthritis but can also appear in other autoimmune diseases like lupus, Sjogren’s syndrome, or chronic infections. It may not appear in everyone with rheumatoid arthritis, so other tests are needed for diagnosis.

Reference range

NCBI: pH 7.35-7.45N/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Rheumatoid Factor (RF)

Frequently asked questions

What does a positive rheumatoid factor mean?
A positive result means your blood contains higher-than-normal levels of rheumatoid factor, which may signal an autoimmune condition. However, it doesn’t confirm a diagnosis alone—your doctor will consider other factors, including symptoms and test results.
Can rheumatoid factor test results change over time?
Yes, rheumatoid factor levels can fluctuate. They may rise during disease activity or flare-ups and sometimes decrease with treatment. Your doctor may retest periodically to monitor changes.
Is this test always accurate?
No, there’s a small chance of false positives, especially in older adults or those with certain infections. False negatives can also occur, so doctors rely on results alongside clinical findings for accurate diagnosis.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 17, 2026. · Read our editorial policy