Table 3.
Diagnostic accuracy† and odds ratio (OR) of RA-related antibodies in prediagnosis serum samples for future RA. Positivity for RF defined on clinical recommendations as present in <5% of 491 healthy blood donors: RF >24.4 units/mL; RF-IgM >13.6 units/mL; RF-IgG >10.9 units/mL; RF-IgA >10.5 units/mL. Positivity for anti-CCP2 based on manufacturer specifications at >5 units/mL. Positivity for anti-CarP defined as ≥2 SD above the mean in healthy controls reserved to define cutoff: anti-CarP-FCS >427.4 units/mL; anti-CarP-Fib >233.9 units/mL.
| Antibody | RA (+/76) |
Cont. (+/41) |
SN (%) |
SP (%) |
OR | 95% CI | p |
|---|---|---|---|---|---|---|---|
| Anti-CCP2 | 34/76 | 0/41 | 44.7 | 100.0 | NA | NA | NA |
| RF | 27/76 | 1/41 | 35.5 | 97.6 | 22.04 | 2.87–169.36 | <0.01 |
| RF IgM | 32/76 | 5/41 | 42.1 | 87.8 | 5.24 | 1.85–14.82 | <0.01 |
| RF IgG | 11/76 | 3/41 | 14.5 | 92.7 | 2.14 | 0.56–8.17 | 0.26 |
| RF IgA | 30/76 | 3/41 | 39.5 | 92.7 | 8.26 | 2.34–29.19 | <0.01 |
| ≥1 RF* | 43/76 | 9/41 | 56.6 | 78.1 | 4.63 | 1.95–11.03 | <0.01 |
| ≥2 RF* | 29/76 | 3/41 | 38.2 | 92.7 | 7.82 | 2.21–27.64 | <0.01 |
| Anti-CarP-FCS | 20/76 | 2/41 | 26.3 | 95.1 | 6.96 | 1.54–31.50 | <0.01 |
| Anti-CarP-Fib | 12/76 | 2/41 | 15.8 | 95.1 | 3.66 | 0.78–17.23 | 0.08 |
| Anti-CCP2 and/or ≥1 RF* | 48/76 | 9/41 | 63.2 | 78.1 | 6.10 | 2.54–14.61 | <0.01 |
| Anti-CCP2 and/or ≥1 RF* and/or anti-CarP-FCS | 49/76 | 11/41 | 64.5 | 73.2 | 4.95 | 2.15–11.41 | <0.01 |
| Anti-CCP2 and/or ≥2 RF* | 41/76 | 3/41 | 53.9 | 92.7 | 14.84 | 4.21–52.25 | <0.01 |
| Anti-CCP2 and/or ≥2 RF* and/or anti-CarP-FCS | 43/76 | 5/41 | 56.6 | 87.8 | 9.38 | 3.32–26.53 | <0.01 |
RA cases positive for RF and/or CCP2 sample n=166, avg. sample/subject=2.5; controls sample n=135, avg. sample/subject=3.3.
Contains the following statistics: sensitivity (SN), specificity (SP).
Count of RF by nephelometry and RF isotypes (IgM, IgG, IgA).
NA: OR, 95% CI, and p cannot be calculated because no controls met positivity criteria.