From the Guidelines
When a patient has a normal ESR and normal protein levels but an elevated rheumatoid factor (RF) of 180, the most important test to run next is anti-cyclic citrullinated peptide (anti-CCP) antibodies, also known as anti-citrullinated protein antibodies (ACPA), as it is more specific for RA than RF and can help establish the diagnosis when combined with RF results 1. This recommendation is based on the evidence that ACPA and RF are predictive of RA diagnosis and prognosis, and that the presence of ACPA or RF increases the probability of developing persistent synovitis or a worse radiographic outcome 1.
Additional Tests
Other recommended tests include:
- Complete blood count (CBC) to check for anemia
- Comprehensive metabolic panel to assess organ function
- C-reactive protein (CRP) as an alternative inflammatory marker
- Imaging studies such as X-rays of hands and feet to look for joint damage
- Joint ultrasound or MRI may provide more detailed information about inflammation and early erosions These tests are necessary because RF can be elevated in conditions other than RA, including other autoimmune diseases, chronic infections, and even in some healthy individuals 1.
Clinical Evaluation
A comprehensive clinical evaluation by a rheumatologist is also essential, as the diagnosis of RA relies on a combination of laboratory findings, imaging results, and clinical symptoms such as joint pain, swelling, and morning stiffness 1.
Key Points
- ACPA is more specific for RA than RF
- RF can be elevated in conditions other than RA
- A comprehensive clinical evaluation is essential for diagnosis
- Imaging studies and laboratory tests are necessary to confirm or rule out RA 1
From the Research
Additional Tests for Elevated Rheumatoid Factor
When Erythrocyte Sedimentation Rate (ESR) and protein are within normal limits (WNL) but Rheumatoid Factor (RF) is elevated at 180, several additional tests can be indicated to support the diagnosis and management of rheumatoid arthritis (RA). These include:
- Anti-cyclic citrullinated peptide (anti-CCP) antibody test, which has been shown to be more specific than RF for the diagnosis of RA 2, 3
- C-reactive protein (CRP) test, which can help assess disease activity and monitor treatment response 2, 4
- Complete blood count (CBC) and radiological examination, such as plain X-ray of hands and feet, to evaluate joint damage and disease severity 5
- Serum 14-3-3η level test, which has been identified as a valuable marker for the diagnosis of RA and may have prognostic value 5
Rationale for Additional Tests
The rationale for these additional tests is based on the understanding that:
- Elevated RF is not exclusive to RA and can be present in other conditions, making it essential to use a combination of tests to confirm the diagnosis 6
- Anti-CCP antibody test can help differentiate between RA and other conditions, and its combination with RF can improve diagnostic accuracy 2, 3
- CRP and ESR tests can provide information on disease activity and help monitor treatment response, although they may not be elevated in all patients with RA 2, 4
- Serum 14-3-3η level test can help predict RA and reflect disease severity and joint damage, making it a valuable addition to the diagnostic panel 5