Table 4.
Diagnostic accuracy† and odds ratio (OR) of RA-related antibodies in serum samples at different time intervals during the prediagnosis period for future RA. Positivity defined as ≥2 SD above the mean in healthy controls reserved to define cutoff: RF-Neph >24.0 units/mL; RF-IgM >13.5 units/mL; RF-IgG >25.0 units/mL; RF-IgA >17.5 units/mL; anti-CCP2 >0.6 units/mL; anti-CarP-FCS >427.4 units/mL; anti-CarP-Fib >233.9 units/mL.
| Antibody | RA (+/n) |
Cont. (+/n) |
SN (%) |
SP (%) |
OR | 95% CI | p |
|---|---|---|---|---|---|---|---|
|
≥0 to ≤1 year before RA Diagnosis (RA cases sample n=23, avg. sample/subject=1; controls sample n=37, avg. sample/subject=1.3) | |||||||
| Anti-CCP2 | 14/23 | 2/28 | 60.9 | 92.9 | 20.22 | 3.83–106.81 | <0.01 |
| ≥1 RF* | 15/23 | 4/28 | 65.2 | 85.7 | 11.25 | 2.88–43.95 | <0.01 |
| ≥2 RF* | 8/23 | 2/28 | 34.8 | 92.9 | 6.93 | 1.30–37.01 | 0.02 |
| Anti-CarP-FCS | 7/23 | 2/28 | 30.4 | 92.9 | 5.69 | 1.05–30.85 | 0.04 |
| Anti-CarP-Fib | 5/23 | 1/28 | 21.7 | 96.4 | 7.49 | 0.81–69.62 | 0.08 |
| Anti-CCP2 and/or ≥1 RF* | 17/23 | 5/28 | 73.9 | 82.1 | 13.03 | 3.41–49.88 | <0.01 |
| Anti-CCP2 and/or ≥1 RF* and/or anti-CarP-FCS | 17/23 | 7/28 | 73.9 | 75.0 | 8.50 | 2.40–30.09 | <0.01 |
| Anti-CCP2 and/or ≥2 RF* | 16/23 | 4/28 | 69.6 | 85.7 | 13.71 | 3.44–54.61 | <0.01 |
| Anti-CCP2 and/or ≥2 RF* and/or anti-CarP-FCS | 16/23 | 6/28 | 69.6 | 78.6 | 8.38 | 2.36–29.74 | <0.01 |
|
>1 to ≤5 years before RA Diagnosis (RA cases sample n=81, avg. sample/subject=1.7; controls sample n=40, avg. sample/subject=1.4) | |||||||
| Anti-CCP2 | 25/49 | 1/29 | 51.0 | 96.6 | 29.17 | 3.67–231.56 | <0.01 |
| ≥1 RF* | 22/49 | 4/29 | 44.9 | 86.2 | 5.09 | 1.54–16.84 | <0.01 |
| ≥2 RF* | 13/49 | 1/29 | 26.5 | 96.6 | 10.11 | 1.25–81.99 | 0.03 |
| Anti-CarP-FCS | 9/49 | 0/29 | 18.4 | 100.0 | NA | NA | NA |
| Anti-CarP-Fib | 6/49 | 1/29 | 12.2 | 96.6 | 3.91 | 0.45–34.24 | 0.22 |
| Anti-CCP2 and/or ≥1 RF* | 32/49 | 5/29 | 65.3 | 82.8 | 9.04 | 2.92–27.94 | <0.01 |
| Anti-CCP2 and/or ≥1 RF* and/or anti-CarP-FCS | 32/49 | 5/29 | 65.3 | 82.8 | 9.04 | 2.92–27.94 | <0.01 |
| Anti-CCP2 and/or ≥2 RF* | 28/49 | 2/29 | 57.1 | 93.1 | 18.00 | 3.84–84.26 | <0.01 |
| Anti-CCP2 and/or ≥2 RF* and/or anti-CarP-FCS | 29/49 | 2/29 | 59.2 | 93.1 | 19.57 | 4.18–91.76 | <0.01 |
|
>5 years before RA Diagnosis (RA cases sample n=89, avg. sample/subject=1.9; controls sample n=57, avg. sample/subject=2.1) | |||||||
| Anti-CCP2 | 15/48 | 1/27 | 31.3 | 96.3 | 11.82 | 1.46–95.37 | 0.02 |
| ≥1 RF* | 20/48 | 3/27 | 41.7 | 88.9 | 5.71 | 1.51–21.60 | 0.01 |
| ≥2 RF* | 8/48 | 0/27 | 16.7 | 100.0 | NA | NA | NA |
| Anti-CarP-FCS | 8/48 | 1/27 | 16.7 | 96.3 | 5.20 | 0.61–44.05 | 0.14 |
| Anti-CarP-Fib | 5/48 | 1/27 | 10.4 | 96.3 | 3.02 | 0.33–27.33 | 0.32 |
| Anti-CCP2 and/or ≥1 RF* | 23/48 | 4/27 | 47.9 | 85.2 | 5.29 | 1.59–17.62 | <0.01 |
| Anti-CCP2 and/or ≥1 RF* and/or anti-CarP-FCS | 24/48 | 5/27 | 50.0 | 81.5 | 4.40 | 1.43–13.54 | <0.01 |
| Anti-CCP2 and/or ≥2 RF* | 16/48 | 1/27 | 33.3 | 96.3 | 13.00 | 1.62–104.58 | 0.02 |
| Anti-CCP2 and/or ≥2 RF* and/or anti-CarP-FCS | 17/48 | 2/27 | 35.4 | 92.6 | 6.86 | 1.45–32.52 | 0.02 |
†
Contains the following statistics: sensitivity (SN), specificity (SP).
*
Count of RF by nephelometry and RF isotypes (IgM, IgG, IgA); individual RF antibodies not presented to save space.
NA: OR, 95% CI, and p cannot be calculated because no controls met positivity criteria.