Anti-CCP antibodies: what they are, what they tell you and when they’re tested

Anti-CCP antibodies, also called ACPA, are antibodies against some of your body’s own proteins once they have been modified. They are the most specific blood test for rheumatoid arthritis: if they are positive and your joints are swollen, the diagnosis is very likely.

When they’re tested

Doctors order them when you have one or more swollen, painful joints with no clear cause, especially in the hands, wrists or feet. Usually together with rheumatoid factor.

They also help predict how the disease may behave: people who test positive tend to have a more aggressive arthritis, which needs early treatment.

It is not a test for people who feel well and have no joint pain. That is why Rosa does not test them. Instead it looks at high-sensitivity CRP, which flags inflammation, and your blood count.

What they tell you, and what they do not

They are positive in about two in three people with rheumatoid arthritis. In people without the disease they are rarely positive, far less often than rheumatoid factor.

They can appear years before the first pain. A positive anti-CCP with no symptoms means a higher risk, not that the disease will certainly come.

If they are negative, rheumatoid arthritis is not ruled out: about one in three people with the disease test negative.

That is why they are read together with other tests:

• Rheumatoid factor: Together with anti-CCP it makes the diagnosis sharper
• High-sensitivity CRP: It shows whether there is active inflammation
• ESR: The other classic inflammation test
• Haemoglobin: Long-lasting inflammation can cause anaemia

Normal anti-CCP levels

There is no single value for everyone. Each lab, depending on the kit it uses, prints a limit on the report: below it is negative, above it positive.

How far above matters. Rheumatologists separate a low positive, up to three times the limit, from a high positive, more than three times. A high positive weighs more.

You do not need to fast, and common medicines do not change the result.

If your anti-CCP is positive or negative

• Positive anti-CCP: With swollen joints, rheumatoid arthritis is very likely and should be treated early. Without symptoms, your doctor follows you over time.
• Negative anti-CCP: Reassuring, but it does not rule out arthritis. Your symptoms and an examination count.

Why anti-CCP can be positive

The most common causes come first.

• Rheumatoid arthritis: By far the most frequent cause when joints are swollen.
• A phase before the disease: In some people they appear years before symptoms. Not everyone goes on to develop it.
• Other autoimmune conditions: Less often they are positive in other kinds of arthritis, lupus or Sjögren’s syndrome, usually at low levels.
• Some lung conditions: Chronic lung inflammation can come with a positive anti-CCP.

When to worry

Talk to your doctor if:

• Your anti-CCP is positive and you have swollen or painful joints: ask for an early rheumatology appointment, because early treatment protects your joints.
• It is positive even without symptoms: your doctor decides whether and when to recheck, and tells you which signs to watch for.
• You have morning stiffness that lasts a long time, or struggle to make a fist.
• You have a joint that suddenly turns red, hot and very painful with a fever: call 112 or go to the emergency department.

Frequently asked questions

What does a positive anti-CCP mean? If you have swollen joints, rheumatoid arthritis is very likely. If you have no symptoms, your risk of developing it is higher, but it is not a certainty. Either way, talk to your doctor.

What are normal anti-CCP levels? It depends on the lab’s kit. Your report prints a limit: below it is negative, above it positive. More than three times the limit is a high positive.

Negative anti-CCP but positive rheumatoid factor: what does it mean? Rheumatoid factor alone is less specific: it can come from infections, other conditions or age. If you have symptoms, your doctor looks at the whole picture with an examination and other tests.

Can anti-CCP turn negative? Sometimes it falls with treatment, but it often stays positive. It is not usually used to follow how the disease is going.

Does Rosa test anti-CCP antibodies? No. Rosa measures high-sensitivity CRP and your blood count, which show whether there is inflammation. If your doctor wants anti-CCP, they order it separately.

Sources

• Nishimura and colleagues, meta-analysis: diagnostic accuracy of anti-cyclic citrullinated peptide antibody and rheumatoid factor for rheumatoid arthritis. Annals of Internal Medicine, 2007. PMID 17548411
• Rantapää-Dahlqvist and colleagues, antibodies against cyclic citrullinated peptide and IgA rheumatoid factor predict the development of rheumatoid arthritis. Arthritis and Rheumatism, 2003. PMID 14558078
• Aletaha and colleagues, 2010 rheumatoid arthritis classification criteria: an ACR/EULAR collaborative initiative. Arthritis and Rheumatism, 2010. PMID 20872595