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 years520723 99610 16767827047
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 psoriasis0256613
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)NANAREF1.50 (0.48 to 4.64)3.12 (1.05 to 9.28)
Further adjusted for calendar year and smokingNANAREF1.30 (0.42 to 4.03)4.55 (1.72 to 12.05)
Age-adjusted and sex-adjusted IRR (anti-TNF treatment only)NANA0.67 (0.22 to 2.07)REF2.08 (0.70 to 6.20)
Further adjusted for calendar year and smokingNANA0.77 (0.25 to 2.40)REF3.51 (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.