Anti-CCP value: what this rheumatoid marker does and does not say

Your anti-CCP value sits on the report, and the question is what that number is worth. Anti-CCP is the most specific rheumatoid marker we currently have: around 95 percent specificity, against roughly 85 percent for rheumatoid factor (PMID 17548411).

The number that rarely comes with it is the sensitivity. That sits near 67 percent. So the test misses roughly a third of the people who really do have rheumatoid arthritis.

My point: that second number belongs in the first paragraph, not in a footnote at the bottom. A negative anti-CCP does not take rheumatoid arthritis off the table.

What is anti-CCP?

Anti-CCP are antibodies against cyclic citrullinated peptides. Your immune system targets your own proteins after a small chemical change, a process called citrullination. In rheumatoid arthritis these antibodies are found relatively often. They are measured in blood and reported in U/ml.

Citrullination itself is not a disease. It happens in inflamed tissue, in the lungs of smokers and in other places in the body.

In some people the immune system starts to treat those altered proteins as foreign. Antibodies against them follow. Why that happens in one person and not in another has not been fully explained.

The test is sometimes called anti-CCP2 or ACPA. That covers the same family of antibodies, measured with a slightly different method.

Your GP works with the NHG standards and refers you to a rheumatologist when inflammatory rheumatic disease is suspected. Thuisarts, the Dutch patient site built on those same standards, describes that route in plain language. Blood testing is a tool along the way, not the end point.

What is a normal anti-CCP value?

A normal anti-CCP value sits below the cut-off used by the laboratory that analysed your blood. That threshold differs per assay, so no universal number exists. Always read the reference range printed next to your own result, usually expressed in U/ml.

That sounds sloppy, but it is the honest answer. A value of 20 U/ml can be called negative by one lab and weakly positive by another.

Rheumatologists also look at how high the result is, not only at positive or negative. In the 2010 classification criteria a low-positive value carries less weight than a high-positive one. High-positive there means more than three times the upper limit of normal (PMID 20872595).

A mildly raised result is therefore not the same as a strongly raised one. Both belong with your GP, not with a conclusion you draw yourself.

What does a positive anti-CCP value mean?

A positive anti-CCP value adds weight, but it is not a diagnosis. In the 2010 classification, serology is one of four domains, alongside joints, inflammation markers and how long your symptoms have lasted. You need at least 6 of 10 points, so blood alone never classifies rheumatoid arthritis (PMID 20872595).

That has a practical consequence. Without swollen joints, a positive anti-CCP simply does not get you to those six points.

Take two people with the same anti-CCP of 60 U/ml. One has had swollen, stiff fingers for months that need an hour every morning to loosen up. The other feels nothing at all and had blood drawn out of curiosity.

Same number, a completely different conversation in the consulting room.

For the first person the result strengthens a picture that was already there. For the second there is a risk signal, and nothing more. What it is worth is weighed by the doctor, together with your symptoms and your joints.

How that weighing works sits in more detail in recognising rheumatoid arthritis: symptoms, blood values and when testing makes sense.

Can anti-CCP be positive without rheumatoid arthritis?

Yes, it can. A specificity of around 95 percent means that roughly 5 in 100 people without rheumatoid arthritis still test positive (PMID 17548411). A positive anti-CCP without symptoms is therefore a reason for a conversation with your GP, not a verdict about your future.

There is a second explanation, and it is the more striking one.

In a Dutch study among blood donors, rheumatoid factor or anti-CCP was already detectable in some future patients before their first symptom. The median lead time was 4.5 years, with a range of 0.1 to 13.8 years (PMID 14872479).

That is not a crystal ball. The study looked back at people who later developed rheumatoid arthritis. It says little about how often someone with a positive result simply stays well.

So that is how I read the figure: as a sign that the immune system starts early, not as a prediction for one person. If you have a positive result without symptoms, there is no need to panic. There is a reason to discuss it.

Antibodies against citrullinated proteins can also turn up in some other conditions. That is another reason never to sail on one number.

Anti-CCP or rheumatoid factor: which says more?

They catch about the same share of patients, but they fail differently. Sensitivity sits close together (67 against 69 percent), while anti-CCP is clearly more specific: 95 against 85 percent. A positive anti-CCP therefore weighs more heavily than a positive rheumatoid factor (PMID 17548411).

The figures come from a 2007 meta-analysis that placed both tests side by side (PMID 17548411).

The combination says more than either number alone. Both positive makes rheumatoid arthritis more likely than one of the two. Both negative still does not rule it out, because seronegative rheumatoid arthritis is real.

That last point is where consumer pages step over the problem too easily. Clean serology feels like a green light, and it is not one.

What a positive or negative rheumatoid factor means on its own sits in rheumatoid factor: what a positive or negative result means. If you are thinking of a broader autoimmune condition, the ANA blood test is the logical next step.

What do you do with your anti-CCP result?

You take it to your GP, together with your symptoms. Are there swollen joints, morning stiffness that lingers, or joint complaints that have run on for weeks? Then that is the conversation, and the result is one part of it.

Without symptoms, the result is mostly information. It asks for context, not for panic.

If you want to know what this marker measures and how we report it, read the page on anti-CCP. If you would rather assemble a test around the markers that fit your own question, you can do that by building your own blood test.

What I think of this marker: it is useful because it raises few false alarms, and it misleads the moment you read it as a final verdict. A rheumatoid arthritis diagnosis is made by a GP or a rheumatologist, with your joints and your story in the room. A blood value adds weight to that picture, or takes weight away.

References

1. Nishimura K, Sugiyama D, Kogata Y, et al. Meta-analysis: diagnostic accuracy of anti-cyclic citrullinated peptide antibody and rheumatoid factor for rheumatoid arthritis. Ann Intern Med. 2007;146(11):797-808. PMID 17548411.
2. Aletaha D, Neogi T, Silman AJ, et al. 2010 Rheumatoid arthritis classification criteria. Arthritis Rheum. 2010;62(9):2569-2581. PMID 20872595.
3. Nielen MM, van Schaardenburg D, Reesink HW, et al. Specific autoantibodies precede the symptoms of rheumatoid arthritis: a study of serial measurements in blood donors. Arthritis Rheum. 2004;50(2):380-386. PMID 14872479.
4. NHG and Thuisarts. Information for GPs and patients on joint complaints, arthritis and rheumatic disease. Available via nhg.org and thuisarts.nl.

Every blood test result at Vitalcheck includes a professional assessment by a BIG-registered doctor. A blood value is not a diagnosis: always discuss treatment decisions with your GP.