In a comparative study (in 2007), various detection kits had a sensitivity between 69.6% and 77.5% and a specificity between 87.8% and 96.4%. Despite the excellent performance of these immunoassays, for example CCP-assays, they only provide a sensitivity comparable with that of rheumatoid factor (RF). Moreover, analysis of the correlation of anti-CCP antibody titre with RA disease activity yielded conflicting results. Unfortunately, these artificial antigens are not expressed in the affected tissue, and therefore are probably not directly involved in the pathogenesis of RA. However, novel test systems utilizing ACPA have been developed.<unk>  vimentin is a very promising autoantigen in RA, and a suitable tool for studying this systemic autoimmune disease. Vimentin is secreted and<unk>  by macrophages in response to apoptosis, or by pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha). A newly developed ELISA system utilises genetically modified<unk>  vimentin (MCV), a naturally occurring isoform of vimentin to optimize the performance of the test. Noteworthy are the findings of a recently published study that highly valuates anti-MCV test systems for diagnosing rheumatoid arthritis in anti-CCP-negative patients. However, data from all around the world vary substantially. Anti-CCP is also very useful in the early diagnosis of rheumatoid arthritis in high-risk groups, such as relatives of RA patients, although Silman and co-workers found that the concordance rate of developing RA was 15.4% among identical (monozygotic) twins and was 3.6% among fraternal (dizygotic) twins. Given that ACPA are more specific than rheumatoid factor, they are used to distinguish various causes of arthritis. Novel assays may be useful for monitoring disease activity and effects of RA therapy. The reference ranges for blood tests of<unk> es are: Negative Low/weak positive Moderate positive High/strong positive Unit 60 EU
Anti–citrullinated protein antibody
Anti-neutrophil cytoplasmic antibody
Anti-nuclear antibody
Anti–Saccharomyces cerevisiae antibody
Antisperm antibodies
Rheumatoid factor
C-ANCA
ANA-12