Analytical performance characteristics of the assays.
| Characteristic | Anti-CCP2, U | Anti-CCP3, U | AxSYM Anti-CCP, U/ml | Anti-MCV, U/ml | RF, IU/ml |
|---|---|---|---|---|---|
| Measuring range | 0–250 | 0–250 | 0–200 | 0–1000 | 10–600 |
| Lower detection limit | 1.4 | 3.6 | 1.0 | 1.0 | 10 |
| Total intraassay CV, % | 6.4 | 3.1 | 6.7 | 2.2 | 5.5 |
| Total intraassay CV, % | 6.9 | 4.1 | 8.6 | 2.3 | 4.1 |
| Method comparison, r | 0.407 | 0.472 | 0.423 | 0.375 | |
| Reference limits (reported by the manufacturers) | < 20: negative, 20–39: weak positive, 40–59: moderate positive, ≥ 60: strong positive | < 5 | < 20: negative, ≥ 20: positive | < 15 | |
CV: coefficient of variation; the runs were performed at 2 different concentrations for each assay and the mean values were estimated; r: Pearson correlation value compared to RF-IgM assay. CCP: cyclic citrullinated peptide; MCV: mutated citrullinated vimentin; RF: rheumatoid factor.