Blood test could provide an early arthritis warning
The researchers took blood samples from these people and samples of the fluid in the joints (synovial fluid) from those with early-stage arthritis. They used advanced laboratory techniques to measure the amount of different proteins in these fluids. They particularly looked at the amount of:
- anti-cyclic citrullinated peptide (CCP) antibodies - a marker for RA
- citrullinated protein - a marker for inflammation
- hydroxyproline - a building block that is part of the protein collagen - a structural protein found in cartilage and bone
They compared the levels of these markers in people from the different groups. They also assessed whether looking for a particular combination of levels of these markers would allow them to tell the different groups apart.
What were the basic results?
The researchers found that compared to healthy controls, blood levels of citrullinated proteins were increased in people with early OA and early RA. Generally, people with early arthritis tended to have higher levels of these proteins in the blood, while in advanced disease, levels were lower in the blood and higher in the joint fluid.
Levels of citrullinated proteins were not increased in people with other non-RA early-stage inflammatory arthritis.
Anti-CCP antibodies were found mainly in the blood of people with early RA.
Compared to health controls, increased levels of hydroxyproline were found in people with early OA and early non-RA, but not in people with early RA.
The researchers found that looking at the levels of all three proteins enabled them to discriminate between people with early OA, early RA, other non-RA early inflammatory arthritis, and healthy joints. This combination test correctly identified:
- 73% of people with early OA
- 57% of people with early RA
- 25% of people with non-RA early inflammatory arthritis
- 41% of people with healthy joints
The test also correctly identified:
- 87% of people who did not have early OA
- 91% of people who did not have early RA
- 76% of people who did not have non-RA early inflammatory arthritis
- 75% of people who did not have healthy joints
How did the researchers interpret the results?
The researchers say their study provides a novel biochemical blood test that could be used for the diagnosis and discrimination of early-stage arthritis. They say that this could help to support improved treatment and patient outcomes.
This laboratory study suggests that for people presenting with early joint symptoms, examining blood levels of a combination of proteins could help to distinguish people who have early-stage OA from those who have early-stage RA or other inflammatory arthritis.
However, this study is in the early stages and so far has only looked at relatively small samples of people with confirmed diagnoses of these different conditions. A lot of further work needs to be done to examine the accuracy of such a blood test, and to see whether it could reliably identify and distinguish between people with these conditions presenting to doctors in real world practice. These studies should assess whether it offers an improvement on the current approach to diagnosis based on symptoms, clinical examination, imaging findings and other blood tests currently used - such as measurement of inflammatory markers, rheumatoid factor, or anti-CCP antibodies.
Even if such studies find that the test performs well, it is likely that it would not replace all other diagnostic tests, instead being used in combination with other methods, especially as it performed better at detecting some forms of arthritis than others.
Most importantly, it also needs to be seen whether using this blood test as a diagnostic method would actually lead to improved disease outcomes for people with arthritis, as suggested in the news reports.
While several of the risk factors associated with OA are unavoidable (e.g. increasing age, female gender, previous joint damage or abnormalities), maintaining a healthy weight and staying active could help prevent onset of the disease. RA is an autoimmune disease (where the body's own immune cells attack the joints) with no established cause. However, smoking is associated with the development of the condition.
"Arthritis breakthrough as new test diagnoses condition up to a decade earlier," the Mail Online reports. The test measures proteins linked with arthritis. The study aimed to see whether a blood test could be developed.
Links to Headlines
Arthritis breakthrough as new test diagnoses condition up to a decade earlier - with just a single drop of blood. Mail Online, March 22 2015
DISCOVERY of proteins could lead to diagnosis of arthritis up to ten years before symptoms. Daily Express, March 22 2015
Links to Science
Ahmed U, Anwar A, Savage RS, et al. Biomarkers of early stage osteoarthritis, rheumatoid arthritis and musculoskeletal health. Scientific Reports. Published online March 19 2015
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