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Anti-CarP antibodies elevated in pre-symptomatic, developed RA
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Anti-carbamylated protein was associated with disease development in patients with rheumatoid arthritis, was shown to increase significantly in patients before symptom development and diagnosis, and correlated with radiographic progression later, according to results from a study of Swedish patients.
Researchers analyzed stored blood samples from 58 men and 194 women collected up to 13 years prior to diagnosis from the Medical Biobank of Northern Sweden and Maternity cohort. Two blood samples were available for 46 patients, 24 patients had three available samples, 13 had four samples, seven had five samples and two patients had six stored samples available.
Median amount of time before symptom onset was 3.5 years, and median sample age was 5.2 years. From the same cohort, the researchers identified 197 patients with stored blood samples available who did not develop rheumatoid arthritis (RA) later.
The samples were analyzed for the content of 10 anti-citrullinated peptide antibodies (ACPA) of the immunoglobulin G (IgG) isotype and anti-carbamylated protein (anti-CarP).
Statistical analysis of the results showed anti-CarP levels in pre-symptomatic patients with RA were elevated compared with the control individuals, with a median of 44 AU/mL vs. 8 AU/mL. Levels continued to increase after the onset of disease activity and symptoms, according to the researchers.
Anti-CarP antibodies were seen in 13.9% of all participants, 18.3% of patients with RA who were pre-symptomatic and 42.2% of patients after developing RA.
The researchers found anti-CarP antibodies were detected more frequently the closer in time to the onset of symptoms that the samples were collected. Among the patients who were pre-symptomatic, 21.8% were observed to have anti-CarP antibody levels above the cut-off value less than 2 years before the onset of symptoms, whereas 18.6% of patients with samples analyzed less than 3 years before disease onset had levels above the cut-off. However, the gradual increase was not considered significant during the pre-dating period, according to the researchers.
The presence of anti-CarP at any time was associated with an odds ratio of 7.1 for later developing RA. Adjusted for covariates such as age, smoking status, sex-specific ACPA peptides did not alter the association. – by Shirley Pulawski
Disclosure: The researchers report no relevant financial disclosure.
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