| Detectability | Positivity* | |||
| RA case sera (n = 49) % (N) | Control sera (n = 245) % (N) | RA case sera (n = 49) % (N) | Control sera (n = 245) % (N) | |
| Anti-IL-1α IgG | 8 (4) | 15 (36) | 2 (1) | 5 (12) |
| IL-1α | 10 (5) | 9 (22) | 6 (3) | 5 (12) |
| IL-1β | 6 (3) | 10 (25) | 4 (2) | 5 (12) |
| IL-1RA | 31 (15) | 22 (53) | 6 (3) | 5 (12) |
| IL-2 | 35 (17) | 45 (110) | 2 (1) | 5 (12) |
| IL-4 | 8 (4) | 3 (8) | 8 (4) | 3 (8) |
| IL-5 | 0 (0) | 2 (4) | 0 (0) | 2 (4) |
| IL-6 | 8 (4) | 7 (18) | 2 (1) | 5 (12) |
| IL-8 | 82 (40) | 81 (199) | 2 (1) | 5 (12) |
| IL-10 | 2 (1) | 5 (13) | 2 (1) | 5 (13) |
| IL-12P70 | 12 (6) | 11 (28) | 4 (2) | 5 (12) |
| TNF-α | 6 (3) | 2 (6) | 6 (3) | 2 (6) |
| TNF-RI | 98 (48) | 100 (245) | 2 (1) | 5 (12) |
| TNF-RII | 98 (48) | 100 (245) | 4 (2) | 5 (12) |
| Interferon-γ | 8 (4) | 8 (19) | 6 (3) | 5 (12) |
| GM-CSF | 2 (1) | 2 (4) | 2 (1) | 2 (4) |
RA, rheumatoid arthritis; IL, interleukin; TNF, tumour necrosis factor; GM-CSF, granulocyte-macrophage colony-stimulating factor.
*Cut-off value defining positivity is given as the 95th percentile of control sera when 5% or more had detectable levels.