Table 1.
Characteristics of the Pre-Rheumatoid Arthritis Cases and Controls in the Department of Defense Serum Biorepository Study Sample
| Characteristics | Cases (N=291) |
Controls (N=292) |
All (N=583) |
|---|---|---|---|
| Age | |||
| 1st Blood Draw, Mean (SD) | 32.6 (8.1) | 29.7 (7.9) | 31.2 (8.1) |
| 2nd Blood Draw, Mean (SD) | 34.3 (8.3) | 33.5 (7.5) | 33.9 (7.9) |
| Male, N (%) | 140 (48.1) | 140 (47.9) | 280 (48) |
| Race, N (%) | |||
| White | 155 (53.3) | 153 (52.4) | 308 (52.8) |
| Black | 76 (26.1) | 80 (27.4) | 156 (26.8) |
| Other | 60 (20.6) | 59 (20.2) | 119 (20.4) |
| Smoking Status, N (%) | |||
| Ever | 91 (31.3) | 74 (25.3) | 165 (28.3) |
| Never | 191 (65.6) | 168 (57.5) | 359 (61.6) |
| Missing | 9 (3.1) | 50 (17.1) | 59 (10.1) |
| BMI Category, N (%) | |||
| Underweight | 0 (0) | 1 (0.3) | 1 (0.2) |
| Normal | 93 (32) | 45 (15.4) | 138 (23.7) |
| Overweight | 141 (48.5) | 76 (26.0) | 217 (37.2) |
| Obese | 52 (17.9) | 26 (8.9) | 78 (13.4) |
| Missing | 5 (1.72) | 144 (49.3) | 149 (25.6) |
| RA Features | |||
| Age at Diagnosis, Mean (SD) | 35.3 (8.21) | ||
| Seropositive Status, N (%) | |||
| At 1st Blood Draw | |||
| Seropositive | 165 (58.1) | ||
| Seronegative | 82 (28.9) | ||
| Missing | 37 (13.0) | ||
| At 2nd Blood Draw | |||
| Seropositive | 208 (72.5) | ||
| Seronegative | 52 (18.1) | ||
| Missing | 27 (9.41) | ||
| Ever* | |||
| Seropositive | 235 (80.8) | ||
| Seronegative | 56 (19.2) | ||
| Years to RA Diagnosis, Mean (SD) | |||
| From 1st Blood Draw | 2.7 (1.6) | ||
| From 2nd Blood Draw | 1.0 (0.9) |
*
Seropositivity in subsequent analyses based on ever ant-CCP or RF seropositive in medical records or anti-CCP or RF testing on stored samples.