The performance of a point of care test for detection of anti-mutated citrullinated vimentin and rheumatoid factor in early rheumatoid arthritis.

The purpose of this study was to determine the diagnostic performance of a point-of-care test (POCT) for detection of anti-mutated citrullinated vimentin (anti-MCV) and rheumatoid factor (RF) in early rheumatoid arthritis (RA) with 2 years of disease duration or less. Additionally, we evaluated the agreement of these tests when using EDTA whole blood and capillary blood. Patients with RA and other rheumatic disorders were consecutively recruited from the rheumatology outpatient clinic. The POCT for detection of anti-MCV and RF using capillary blood and EDTA whole blood was performed in 78 patients with early RA, 55 patients with other rheumatic disorders, and 55 healthy blood donors. The sensitivity and specificity of anti-MCV POCT in patients with early RA were 64 and 97 %, respectively, while the sensitivity and specificity of RF POCT were 51 and 95 %, respectively. The positive likelihood ratio of the POCT for anti-MCV was higher than those for RF (23.5 vs 9.4). The negative likelihood was 0.37 for anti-MCV and 0.52 for RF. There were three cases with false positive for anti-MCV including a patient with psoriatic arthritis and the other two with systemic sclerosis. The agreement between capillary blood and EDTA whole blood testing for anti-MCV and RF was low to moderate with Cohen's kappa of 0.58 and 0.49, respectively. This POCT for detection of anti-MCV and RF yielded high specificity and may be a valuable tool for the diagnosis of early RA. Using this POCT with EDTA whole blood instead of capillary blood is not recommended.