Morning stiffness that takes a long time to ease. A knuckle that looks puffy for weeks. Tiredness that does not match the week you had. Joint symptoms like these are a common reason people come to see a therapist, and they often lead to a question about blood tests for autoimmunity.
The rheumatoid factor and anti-CCP blood test, along with the ANA test, measures antibodies linked to autoimmune conditions. These tests are useful, but they are only one part of the picture. This guide explains what each test in the BPR catalogue measures and why the clinical examination still comes first.
What "autoimmune" means
The immune system is built to recognise and respond to threats such as bacteria and viruses. In an autoimmune condition, part of that response is directed at the body's own tissues. In rheumatoid arthritis, the main target is the lining of the joints, which becomes inflamed, painful and swollen (Di Matteo et al., 2023). In lupus, the effects can be wider: the NHS lists joint and muscle pain, extreme tiredness and rashes, often after time in the sun, among the main symptoms (NHS, Lupus).
Many of these conditions produce antibodies that a laboratory can measure. That is the idea behind the tests below.
Rheumatoid factor and anti-CCP blood test
Rheumatoid Factor (Latex Test)
Rheumatoid factor is an antibody that, according to LML, is commonly found in people with rheumatoid arthritis. LML explains that the test helps tell rheumatoid arthritis apart from other forms of arthritis and can also be used to follow the condition over time. Rheumatoid factor is not exclusive to rheumatoid arthritis, which is why it is read alongside other information (Motta et al., 2023).
Anti-CCP Antibodies
Anti-cyclic citrullinated peptide (anti-CCP) antibodies are, in LML's words, highly specific to rheumatoid arthritis. In the UK, NICE recommends a rheumatoid factor test for adults with suspected rheumatoid arthritis who have joint swelling (synovitis) on examination, and suggests considering anti-CCP if rheumatoid factor is negative. NICE also notes that anti-CCP antibodies help indicate the likely course of joint changes over time (NICE NG100).
Rheumatology Profile 6 (Rheumatoid Plus)
This LML profile combines three markers in one sample: rheumatoid factor, anti-CCP antibodies and high-sensitivity C-reactive protein. It is a practical option when a clinician wants the two antibodies and an inflammation marker together.
Antinuclear antibodies (ANA)
The Antinuclear Antibodies (Titre & Pattern) test looks for antibodies that target the nucleus of cells. LML explains that the result has two parts: the titre, which reflects how concentrated the antibodies are, and the pattern, which describes how they bind to the nucleus. According to LML, the test can contribute to the assessment of conditions such as systemic lupus erythematosus, Sjögren's syndrome, rheumatoid arthritis and mixed connective tissue disease.
One point surprises many people: a positive ANA can also be found in people who are healthy. International experts stress that ANA results only make sense next to symptoms and examination findings, and that the titre and pattern guide what, if anything, comes next (Bossuyt et al., 2020). LML states that results are available about five days after the sample reaches the laboratory.
CRP and ESR: the general inflammation markers
Two tests are often requested next to the antibodies:
- C-Reactive Protein (High Sensitivity): LML describes it as a measure of the presence and severity of inflammation. It can rise with infections, autoimmune conditions and other causes.
- Erythrocyte Sedimentation Rate (ESR): measures how quickly red blood cells settle in a tube. LML calls it a non-specific test: it tends to be raised in inflammatory conditions such as rheumatoid arthritis and polymyalgia rheumatica, but also in infections and even in pregnancy. LML notes the sample must reach the laboratory within 24 hours.
These markers say "there may be inflammation". They do not say where it comes from.
