Table 4. Comparison of rates of psoriasis by cohort and biological drug compared to disease-modifying antirheumatic drug (DMARD) treatment and within anti-tumour necrosis factor (TNF) treatments compared with etanercept.
| Control (DMARD) (n = 2880) | Anti-TNF (n = 9882) | Specific anti-TNF treatment | |||
| Etanercept (n = 5265) | Infliximab (n = 3569) | Adalimumab (n = 3907) | |||
| Person years | 5207 | 23 996 | 10 167 | 6782 | 7047 |
| Follow-up per person, (years) median (IQR) | 1.91 (0.96 to 2.45) | 2.81 (1.94 to 3.27) | 2.95 (2.43 to 3.28) | 3.07 (1.99 to 4.04) | 1.99 (1.08 to 2.95) |
| No. of psoriasis | 0 | 25 | 6 | 6 | 13 |
| Rate of psoriasis/1000 person years (95% CI) | 0 (0.71†) | 1.04 (0.67 to 1.54) | 0.59 (0.22 to 1.28) | 0.88 (0.32 to 1.93) | 1.84 (0.98 to 3.15) |
| Age-adjusted and sex-adjusted IRR (anti-TNF treatment only) | NA | NA | REF | 1.50 (0.48 to 4.64) | 3.12 (1.05 to 9.28) |
| Further adjusted for calendar year and smoking | NA | NA | REF | 1.30 (0.42 to 4.03) | 4.55 (1.72 to 12.05) |
| Age-adjusted and sex-adjusted IRR (anti-TNF treatment only) | NA | NA | 0.67 (0.22 to 2.07) | REF | 2.08 (0.70 to 6.20) |
| Further adjusted for calendar year and smoking | NA | NA | 0.77 (0.25 to 2.40) | REF | 3.51 (1.32 to 9.31) |
*Hypothetical case of psoriasis for use as comparison; †one-sided 97.5% confidence interval.
IQR, interquartile range; IRR, incidence rate ratio; NA, not applicable; REF, reference value.