Baseline characteristics of seropositive arthralgia patients (SAP) who did (RA+) or did not (RA−) develop rheumatoid arthritis within the follow-up period
| All SAP | RA+ | RA− | p Value RA+ vs RA−* | |
|---|---|---|---|---|
| N | 289 | 94 | 195 | |
| Female (%) | 79 | 81 | 78 | 0.76 |
| Mean age in years (SD) | 50 (12) | 48 (11) | 50 (12) | 0.19 |
| Smoking at inclusion (%) | 29 | 35 | 26 | 0.13 |
| HLA-DRB1 SE (%) | 40 | 45 | 37 | 0.19 |
| Seropositive for IgM-RF (%) | 61 | 57 | 63 | 0.37 |
| Seropositive for IgG ACPA (%) | 65 | 90 | 53 | 0.00 |
| Median (IQR) hsCRP (mg/L) | 2.2 (1.0–4.8) | 2.6 (1.0–4.6) | 2.0 (0.9–5.1) | 0.47 |
| Median (IQR) TJC53 at inclusion | 0 (0–3) | 1 (0–4) | 0 (0–3) | 0.10 |
| Median (IQR) follow-up in months | 30 (13–49) | 25 (12–46) | 34 (15–49) | 0.05 |
| Median (IQR) time until RA development | − | 12 (6–20) | – | – |
| Positive for anti-Porphyromonas gingivalis IgA (%)† | 20 | 11 | 25 | 0.01 |
| Positive for anti-P gingivalis IgG (%)† | 34 | 26 | 37 | 0.05 |
| Positive for anti-P gingivalis IgM (%)† | 6.9 | 5.3 | 7.7 | 0.62 |
*Variables reflected in percentages: Fisher's exact test with two sided p value, other variables: unpaired t test with Welch's correction (Gaussian distribution) or Mann–Whitney test (no Gaussian distribution).
†Positivity is defined as higher than mean+2SD of anti-P gingivalis levels of healthy controls.
ACPA, anticitrullinated protein antibodies, cut-off level for positivity 5 U/mL; HLA-DRB1 SE, one or two copies of the HLA-DRB1*0101, *0102, *0401, *0404, *0405, *0408, *0410 or *1001 alleles; hsCRP, high-sensitivity C-reactive protein; N, number; RA, rheumatoid arthritis; RF, rheumatoid factor, cut-off level for positivity 30 IU/mL; TJC53, tender joint count 53 joints.