RA Factor and Anti-CCP Test: What a Positive Result Means
By Dr. Krishna Adhikari, Consultant Rheumatologist
MBBS, MD (Internal Medicine), Fellowship in Clinical Rheumatology
Awaiting medical review: this new article has not yet been checked by Dr. Krishna Adhikari. It will be updated after his review.
A positive RA factor (rheumatoid factor, RF) or anti-CCP result means that antibody was found in your blood. On its own it does not mean you have rheumatoid arthritis: RF is also positive in some healthy people and in other conditions, anti-CCP is less often positive without the disease, and a doctor decides by combining the report with your symptoms, an examination and other tests. A normal result does not rule it out either.
What are the RA factor and anti-CCP tests done for?
Both are blood tests with no fasting (Testing.com). RF is a protein the immune system makes by mistake or when it is overactive fighting an infection; it attacks healthy cells, not germs (MedlinePlus). The anti-CCP test (also called ACPA) looks for autoantibodies that attack healthy tissue in the joints (MedlinePlus). Doctors use them, often together, to help decide whether joint symptoms are rheumatoid arthritis (MedlinePlus; see our rheumatoid arthritis guide). Neither measures inflammation (Testing.com); ESR and CRP do, see our ESR and CRP guide.
What does a positive RA factor mean?
A positive RF means a higher level of rheumatoid factor was found. On its own it cannot diagnose a condition: many people have small amounts and are healthy (MedlinePlus). The NHS says more than half of people with rheumatoid arthritis have high RF when it starts, but about 1 in 20 people without it also test positive. MedlinePlus lists other causes: Sjögren disease and scleroderma, lupus, hepatitis C, tuberculosis and certain cancers.
What does a positive anti-CCP mean?
MedlinePlus says CCP antibodies are found in most people with rheumatoid arthritis and almost never in people without it, so anti-CCP is called more specific than RF. "Almost never" is not never: a 2007 analysis of 37 anti-CCP and 50 RF studies (Nishimura et al.) found anti-CCP negative in 95% of people without the disease, against 85% for IgM RF, while both caught a similar share of people with it (67% and 69%); the authors note many studies had limitations. Specific does not mean certain: it can also appear in Sjögren disease, lupus, active tuberculosis, chronic lung disease (MedlinePlus) and psoriatic arthritis (Testing.com). With joint symptoms it is a strong signal, not a standalone diagnosis (Testing.com).
Both positive or only one positive: does it matter?
For a person with symptoms of rheumatoid arthritis, MedlinePlus says:
anti-CCP and RF both positive: you probably have it;
anti-CCP positive, RF negative: you may be in the early stages or may develop it;
both negative: you are less likely to have it, and more tests may be needed.
The patient sources we read give no equally simple rule for a positive RF with a negative anti-CCP. A 2014 analysis of 24 studies (Sun et al.) found that when both tests had to be positive, 96% of people without the disease tested negative and 57% of those with it tested positive; when either was enough, 82% and 78%. One positive therefore means more false alarms and needs other examinations to confirm.
Do the numbers have to be high, and what is the normal range?
Positive means above the laboratory's own upper limit of normal (MedlinePlus; Aletaha et al.), so there is no universal cut-off. Labs may report a number, a titre or only positive or negative. For RF, the MedlinePlus encyclopedia gives normal as less than 15 IU/mL or a titre below 1:80, and Cleveland Clinic less than 20 U/mL. Anti-CCP is judged against each lab's own cut-off, and labs may group results as weak, moderate or strong positive (Testing.com). Read the range and units on your own report.
Generally, the higher the RF the more likely a linked condition, but no number settles the question: people with rheumatoid arthritis can have little or no RF, and people without it can have a lot (MedlinePlus). In the 2010 classification criteria, which doctors apply only to people with a swollen joint found on examination and no better explanation, a result above the laboratory's limit but no more than 3 times it is low-level positive and above 3 times it is high-level; an RF reported only as positive counts as low-level, and higher results weigh more (Aletaha et al.; Testing.com).
Can I have rheumatoid arthritis if both tests are negative?
Yes, although two negative results make it less likely (MedlinePlus). The NHS says no blood test can definitively prove or rule out rheumatoid arthritis. Doctors call it seronegative rheumatoid arthritis (Testing.com). In the 2014 analysis above, 78% of people with the disease were positive on at least one of the two tests, so about 1 in 5 had both negative. Testing.com adds that anti-CCP can be negative early on, before antibodies have developed.
Can a positive result turn negative?
Anti-CCP usually stays positive. In a Swedish trial of early rheumatoid arthritis (Kastbom et al.), 139 people were tested over two years: antibody levels fell during the first year of treatment, but the share testing positive barely changed, and only 5 of the 97 who started positive tested negative. Testing.com says anti-CCP may stay positive even when the arthritis is well controlled, and that it is not used to track treatment. We found no source on RF turning negative.
Can the test show I will get arthritis if I have no symptoms?
Not reliably. Both are meant for people with symptoms: Testing.com calls anti-CCP a diagnostic test, not a screening test, and says a positive RF without joint symptoms rarely leads to a rheumatoid arthritis diagnosis. Antibodies can appear years before symptoms: 35% of 71 Swedish blood donors who later developed rheumatoid arthritis had IgG anti-CCP in a sample taken a median 2.5 years before symptoms began (Kokkonen et al.). The NHS diagnosis page (for people with symptoms) says those who test positive for anti-CCP are very likely to develop the disease; Testing.com says the test alone cannot say whether or when. With a positive result and no symptoms, talk to a doctor before drawing conclusions (Testing.com).
What should I do with a positive report?
Do not diagnose yourself from the report, or ignore it. Show it to a doctor, who may refer you to a rheumatologist if results are inconclusive (MedlinePlus). Bring:
the original report with its units and reference range, and any earlier reports;
a list of every medicine, vitamin and supplement you take (MedlinePlus);
notes on which joints hurt, when it started and how long morning stiffness lasts (Arthritis Foundation; see inflammation and stiffness);
whether anyone in your family has rheumatoid arthritis or another autoimmune disease (Arthritis Foundation).
The doctor will examine your joints and may add ESR, CRP and an X-ray, ultrasound or MRI scan (NHS; Arthritis Foundation).
RF र anti-CCP जाँच: नेपालीमा संक्षेप
RF र anti-CCP रगत जाँच हुन्। रुमाटोइड आर्थराइटिस (गठिया बाथ) को निदानका लागि डाक्टरले यी जाँच गराउन सक्नुहुन्छ। RF पोजिटिभ आउँदैमा रुमाटोइड आर्थराइटिस भएको हुँदैन; धेरै स्वस्थ मानिसमा पनि RF पोजिटिभ आउन सक्छ। रुमाटोइड आर्थराइटिस नभएका मानिसमा RF भन्दा anti-CCP कम पोजिटिभ आउँछ, तर अन्य रोगमा पनि आउन सक्छ। दुवै जाँच सामान्य आए पनि यो रोग हुन सक्छ। कुनै एउटा जाँचले मात्र यो रोग पक्का वा रद्द गर्दैन; डाक्टरले लक्षण, शारीरिक जाँच र अन्य परीक्षणका रिपोर्ट हेरेर निदान गर्छन्।
प्रयोगशालाअनुसार दायरा फरक हुन्छ, त्यसैले आफ्नो रिपोर्टमा छापिएको दायरा हेर्नुहोस्। रिपोर्ट पोजिटिभ आए पनि सामान्य आए पनि जोर्नी दुख्ने, सुन्निने वा कडा हुने समस्या ठीक नभएमा, वा बिहान ३० मिनेटभन्दा बढी कडा भइरहेमा, चाँडै बाथ रोग विशेषज्ञ (रुमाटोलोजिस्ट) लाई देखाउनुहोस्। कुनै एउटा जोर्नी अचानक धेरै दुखेर सुन्निएको, तातो वा रातो भएको छ, वा जोर्नी दुख्दा ज्वरो आएको छ भने तुरुन्तै डाक्टरलाई देखाउनुहोस्।
When to see a rheumatologist
Warning signs first. Joint pain with a swollen, hot area of skin around the joint, or with a high temperature, feeling unwell or feeling hot, cold or shivery, needs urgent medical care and can be a joint infection (NHS): see a doctor the same day, or a hospital emergency department if you cannot be seen quickly. Go to a hospital emergency department straight away after very bad joint pain from a fall or injury, or if you cannot put weight on a joint or it has moved out of place (NHS).
See a doctor if joint pain or swelling keeps coming back or is getting worse, or your joints are stiff for more than 30 minutes after waking (NHS). The UK's NICE advises doctors to refer adults with suspected persistent synovitis (inflammation of the joint lining; NIAMS) for a specialist opinion, and urgently, even with negative anti-CCP or RF, if the small joints of the hands or feet are affected, more than one joint is affected, or 3 months or more have passed between the first symptoms and seeking medical advice. These are rules for doctors, not self-diagnosis, but a normal report does not end the question. Long-lasting joint problems are often called bath rog in Nepali; see our bath rog guide.
Rheumatology care in Kathmandu Valley
Rheumatology care at Tulsi Multi Speciality Clinic is provided by Dr. Krishna Adhikari, consultant rheumatologist and Lecturer in Internal Medicine at Patan Academy of Health Sciences (Patan Hospital), NMC No. 13049. He consults Sunday to Friday from 4:00 PM at AVM Chowk, Manbhawan, Lalitpur-5, Kathmandu Valley. See our rheumatology service and Dr. Krishna Adhikari's profile, book an appointment, or call +977-1-5914294. This article is general information, not a substitute for a consultation.
Sources
Rheumatology care at Tulsi Multi Speciality Clinic · Dr. Krishna Adhikari, consultant rheumatologist
To see a doctor, book online, call +977-1-5914294 or message the clinic on WhatsApp.