| Characteristics | Anti-TNF group n = 64 | No anti-TNF group, n = 48 | Healthy controls n = 18 | p Value |
| Women (%) | 73 | 69 | 78 | 0.74* |
| Age, mean (range), years | 51 (23–75) | 46 (18–85) | 47 (21–75) | 0.23† |
| Gastroenterological disease (%) | 9 | 33 | – | 0.002‡ |
| Rheumatoid arthritis (n) | 52 | 27 | ||
| Juvenile chronic arthritis (n) | 2 | 2 | ||
| M. Still (n) | 2 | 0 | ||
| Psoriatic arthritis (n) | 1 | 3 | ||
| Spondyloarthropathy (n) | 1 | 0 | ||
| M. Crohn (n) | 6 | 15 | ||
| Inflammatory bowel disease (n) | 0 | 1 | ||
| Duration of disease activity, mean (months) | 156 | 111 | – | 0.041§ |
| Prednisone (%) | 20 | 23 | – | 0.74‡ |
| Mean daily dose, mg | 7 | 9 | – | 0.58§ |
| Methotrexate (%) | 71 | 75 | – | 0.58‡ |
| Mean weekly dose, mg | 16 | 15 | – | 0.72§ |
| Azathioprine (%) | 8 | 17 | – | 0.15‡ |
| Mean daily dose, mg | 115 | 109 | – | 0.73§ |
| NSAIDs (%) | 57 | 58 | 0.90‡ | |
| Prior vaccination (%) | 62 | 38 | 6 | <0.001* |
*χ2 test (two-sided) for anti-TNF versus no anti-TNF versus healthy controls.
†One-way ANOVA for anti-TNF versus no anti-TNF versus healthy controls.
‡χ2 test (two-sided) for anti-TNF versus no anti-TNF.
§Wilcoxon rank sum test (two-sided) for anti-TNF versus no anti-TNF
TNF, tumour necrosis factor α; NSAIDs, non-steroidal anti-inflammatory drugs; M, morbus.