Table 3.
Comparisons between autoantibody positive and negative individuals who participated in the health-fair IA/RA screen
| Findings | RF and anti-CCP negative N=534* | RF only N=44 | Anti-CCP only N=12 | RF and CCP N=11 |
|---|---|---|---|---|
| Inflammatory arthritis (IA) present** | 58 (10.9%) | 17 (38.6%)(p<0.01) | 1 (8.3%)(p>0.5) | 8 (72.7%)(p<0.01) |
| # meeting ≥4 ACR criteria for RA *** | 0 (0.0%) | 6 (1.4%) | 1 (8.3%) | 2 (18.2%) |
| # with IA, not meeting ≥4 ACR RA criteria** | 58 (10.9%) | 10 (22.7%) | 0 (0%) | 5 (45.5%) |
| # with no IA** | 480 (89.9%) | 27 (61.4%) | 11 (91.7%) | 3 (27.3%) |
| CRP ≥ 0.8 mg/dL | 54 (10.1%) | 5 (11.4%)(p>0.5) | 2 (16.7%)(p=0.35) | 5 (45.5%)(p<0.01) |
| Levels of biomarkers, median (range) | ||||
| CRP | 0.2 (0.0–13.1) | 0.2 (0.1–2.6) | 0.2 (0.1–2.7) | 0.5 (0.1–2.0) |
| RF | 6.0 (2–14) | 25 (15–294) | 7.5 (4–11) | 70 (21–600) |
| Anti-CCP | ≤19 | ≤19 | 29.5 (20–≥60) | ≥60 (33–≥60) |
| Reason for Screening | ||||
| Check-up Only | 28.7% | 25.0% (p>0.5) | 8.3% (p>0.5) | 0% (p=0.04) |
| Relative with RA | 28.3% | 29.5% (p>0.5) | 25.0% (p>0.5) | 9.1% (p=0.31) |
| Symptoms | 48.1% | 63.4% (p=0.06) | 66.7% (p=0.25) | 91.9% (p<0.01) |
| Race | ||||
| White | 89.7% | 77.3% (p=0.02) | 91.7% (p=1.0) | 81.8% (p=0.33) |
| Black | 2.2% | 0% (p>0.5) | 0% (p>0.5) | 0% (p>0.5) |
| Hispanic | 5.1% | 11.4% (p=0.09) | 8.3% (p=0.48) | 9.1% (p=0.45) |
| Asian | 1.1% | 6.8% (p=0.03) | 0% (p>0.5) | 0% (p>0.5) |
| Sex, % Female | 73.8% | 72.7% (p>0.5) | 91.7% (p>0.5) | 45.5% (p>0.5) |
| Mean age (std) | 59.1 (13.4) | 61.0 (12.9)(p=0.38) | 58.9 (11.9)(p>0.5) | 54.5 (7.4)(p=0.24) |
All statistical comparisons are made using the RF and anti-CCP negative group as reference group.
Inflammatory arthritis designated if ≥swollen joint/s present on physical examination; joints counted as swollen included proximal inter-phalageal (PIP) joints of the fingers, metacarpal-phalangeal joints (MCPs), wrists, and elbows.
American College of Rheumatology (ACR) Revised 1987 Criteria for RA (Arnett FC et al, 1988). For this analysis, only 5 of the 7 criteria were assessed as follows: 1) morning stiffness ≥1 hour; 2) hand arthritis, 3) three or more joint areas, and 4) symmetric arthritis determined by joint examination at time of screening; 5) RF and/or anti-CCP positivity by testing at the time of the screen. Subjects with fulfillment of ACR criteria were those with no diagnosis of RA prior to the health-fair.
Abbreviations/units: IA=inflammatory arthritis; RA=rheumatoid arthritis; RF=rheumatoid factor, international units per milliliter (IU/mL); anti-CCP=anti-cyclic citrullinated peptide antibody, units per milliliter (U/mL), only values between 20–59 were reported as discrete integers, levels below/above this range are reported as <20 or ≥60, respectively; CRP=C-reactive protein, milligrams per deciliter (mg/dL); std=standard deviation.