Table 1.
Demographic and clinical characteristics of military cases with rheumatoid arthritis (RA) and controls *
| All Cases (N=83) | Seronegative Cases (N=10) |
Seropositive RA Cases (N=73) |
Controls (for seropositive cases) (N=73)** |
Cases <40 at diagnosis of RA (N=35) |
Cases ≥40 at diagnosis of RA (N=38) |
P- value+ |
|
|---|---|---|---|---|---|---|---|
|
Age at diagnosis,
mean (SD)[range] |
39.9 (10.0)[20.9-66.1] | 39.1 (8.7)[26.4-53.5] | 40.0(10.3)[20.9-66.1] | 39.9 (10.3)[20.9-66.1] | 31.3 (5.6)[20.9-39.7] | 48.1 (6.2)[40.0-66.1] | <0.01 |
| Male | 49 (59.0%) | 6 (60.0%) | 43 (58.9%) | 43 (58.9%) | 17 (48.6%) | 26 (68.4%) | 0.10 |
| Race | |||||||
| White | 57 (68.7%) | 8 (80.0%) | 49 (67.1%) | 49 (67.1%) | 21 (60.0%) | 28 (73.7%) | 0.27 |
| Black | 21 (25.3%) | 2 (20.0%) | 19 (26.0%) | 19 (26.0%) | 10 (28.6%) | 9 (23.4%) | |
| Other*** | 5 (6.0%) | 0 ( 0.0%) | 5 (6.9%) | 5 (6.9%) | 4 (11.4%) | 1 (2.6%) | |
| Erosions, N (%) | |||||||
| Present | 42 (50.6%) | 4 (40.0%) | 38 (52.0%) | n/a | 20 (57.1%) | 18 (47.4%) | 0.48 |
| Pre-Diagnosis Serum Samples (Total samples N=212) |
All Cases | Sero-Negative Cases |
Seropositive Cases | Controls (for seropositive cases) |
Cases <40 at diagnosis of RA (N=35) |
Cases ≥40 at diagnosis of RA (N=38) |
P- value |
|---|---|---|---|---|---|---|---|
| Number of samples per case Mean (SD) [range] |
3.5 (1.2)[1-5] | 3.6 (1.0)[2-5] | 3.5 (1.3)[1-5] | 3.5 (1.3)[1-5] | 3.7 (1.2)[1-5] | 3.2 (1.3)[1-5] | 0.10 |
| Pre-diagnosis samples per case Mean (SD) [range] |
2.9 (1.2)[1-4] | 3.1 (1.0)[1-4] | 2.9 (1.2)[1-4] | 2.9 (1.2)[1-4] | 3.0 (1.1)[1-4] | 2.8 (1.4)[1-4] | 0.41 |
| Time of first collection of samples pre-diagnosis ( in years) Mean (SD) [range] |
6.6 (3.7) [0.06 to 13.67] |
6.4 (2.7) [0.84 to 10.89] |
6.6 (3.9) [0.06 to 13.67] |
6.6 (3.9) [0.04 to 13.71] |
5.8 (3.5) [0.99-13.63] |
7.3 (4.1) [0.06-13.67] |
0.08 |
Sero-positive status indicates that subject met ≥1 of the following criteria: 1) RF positivity by WRAMC testing (RF only, nephelometry or latex agglutination), and/or 2) RF or anti-CCP positivity by testing of post- or immediate pre-diagnosis samples.
Controls were matched to cases by age, based on the age of a case at time of diagnosis of RA. For example, if a case was 40 at time of diagnosis of RA, the corresponding control would be the same age.
Other includes Asian, Native American, and multi-racial subjects
P-values are for comparisons between age-at-diagnosis groups <40, ≥40, using chi-squared or t-tests
Abbreviations: RA=rheumatoid arthritis; SD= standard deviation