Table 1 Characteristics of the study population
| Â | Group | |||
|---|---|---|---|---|
| Â | All RA (n = 308) | IgM RFpos RA (n = 178) | IgM RFneg RA (n = 130) | Controls (n = 605) |
Age in years (mean ± SD and range) | 54.5 ± 14.7 (22 to 93) | 56.2 ± 14.0 (22 to 86) | 52.4 ± 15,4 (23 to 93) | 42.6 ± 12.8 (19 to 65) |
Male/Female | 74/234 | 47/131 | 27/103 | 367/238 |
Serum YKL-40 ng/ml (median and 95% CI) | 86 (79 to 94) | 91 (81 to 102) | 80 (70 to 91) | 46 (44 to 48) |