At the moment there is no blood test for osteoarthritis in the initial stage, a degenerative joint disease in which the cartilage that fades and the movement of the bearings breaks, causing pain, swelling and problems in moving the joint. Currently, magnetic resonance imaging techniques have been developed for evaluation of cartilage damage in early-stage osteoarthritis. These imaging techniques have approximately 70 % sensitivity and 90 % specificity compared to reference diagnosis by arthroscopy. They require expensive instrumentation, time and facilities. They cannot be used in patients with implanted pacemakers or aneurysm coils. Detection of rheumatoid arthritis by clinical chemistry assessments has been improved by introduction of the anti-cyclic citrullinated peptide (CCP) antibody test, which has 68% sensitivity and 98% specificity in established disease. Now, researchers at Warwick University in the UK have developed a blood test that can provide an early diagnosis of osteoarthritis, and distinguish it from rheumatoid arthritis and other inflammatory joint diseases. The new blood test looks for chemical signatures in damaged protein or amino acid fragments. The researchers, led by Dr. Naila Rabbani of Warwick Medical School, report how they developed the new blood test in the journal Arthritis Research & Therapy.
The new blood test looks for chemical signatures in fragments of joint proteins (peptides) that have been damaged, as Dr. Rabbani explains: “The combination of changes in the oxidized, nitrated and modified amino acids with blood sugar allowed the early detection of the stage and classification of arthritis – osteoarthritis, rheumatoid arthritis or other self-resolving joint inflammatory disease: for the first time we measured small fragments of damaged proteins that escaped from the joint into the blood”. For the study, the team recruited 225 participants. These included patients with advanced osteoarthritis, rheumatoid arthritis, rheumatoid arthritis, other inflammatory joint diseases and healthy volunteers without joint problems. Using mass spectrometry, the researchers analyzed samples of blood and synovial fluid (from the affected knee joints) for proteins and amino acids oxidized, nitrated and modified with sugar. They found some models of damaged amino acids in samples of patients with early and advanced osteoarthritis and rheumatoid arthritis that were markedly inferior in samples taken from healthy volunteers. Using sophisticated bioinformatics methods, they developed algorithms – based on 10 damaged amino acids – that can diagnose early arthrosis, rheumatoid arthritis and non-rheumatoid arthritis. The researchers note that the new blood test has a “relatively high sensitivity and specificity for early stage diagnosis and typing of the arthritic disease”.
Sensitivity is the measure in which a negative result is able to exclude the disease, and specificity is the extent to which a positive result can govern the disease. In the case of early stage osteoarthritis, the study found that the blood test had 92% sensitivity and a 90% specificity. These compare favorably with current techniques. For example, in their basic information, the researchers note that current magnetic resonance imaging techniques to evaluate cartilage damage in early arthrosis have sensitivity around 70% and specificity around 90%. In addition, compared to a blood test, these techniques are expensive and time-consuming and can not be used with some patients, such as those with pacemakers. The test could be available within 2 years, the researchers say. As soon as osteoarthritis has been diagnosed – before the physical and irreversible symptoms become established – the greater the chances that treatment will focus on how to prevent the problem, for example with lifestyle changes. Remembering what the test looks for (fragments of proteins or oxidized / nitrated glucose portions), the role of oxidative stress in the pathogenesis of the disease is emphasized, a diet poor in antioxidant factors (vitamin C, polyphenols) or nutrients for blood fluidity (omega-3 from fish), oxidative stress is the factor that emerges from the last corner of the study.
To remind us once again that lifestyle is not an option….when looking for a good health.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Malafoglia V et al., Raffaeli W. Trials. 2017 Dec 19; 18(1):605.
Razny U, Goralska J et al. Acta Biochim Pol. 2017; 64(3):415-422.
Ahmed U et al., Rabbani N. Arthritis Res Ther. 2016 Oct 27;18(1):250.