OBJECTIVES: The efficacy and safety of certolizumab pegol (CZP), a PEGylated anti-TNF, in patients with active Crohn's disease (CD) have been demonstrated in two 26-week induction and maintenance trials, PRECiSE 1 (Sandborn et al., 2005) and PRECiSE 2 (Schreiber et al, 2005). This analysis evaluated the effect of CZP versus placebo on quality-adjusted life-years (QALYs) for each subject in these trials. METHODS: In PRECiSE 1, patients with active CD received double-blind CZP 400 mg (n=331) or placebo (n=328) every 4 weeks after induction. PRECiSE 2 began with an open-label induction period (CZP 400 mg at Weeks 0, 2 and 4). Patients who demonstrated a clinical response at Week 6 were randomised to receive CZP 400 mg (n=215) or placebo (n=210) every 4 weeks from Weeks 8 to 24. The EQ-5D was administered at each visit and converted into utility scores using an established algorithm (Dolan et al, 1995). An estimate of QALYs was made for each patient from the area under the utility curve during the randomisation period of each trial. Mean QALYs and standard deviation (SD) were calculated by treatment group and compared using a Wilcoxon rank sum test. RESULTS: Over the 26-week PRECiSE 1 trial, the mean (SD) QALYs were 0.5456 (0.2993) for CZP and 0.4797 (0.3121) for placebo. Similarly, between Weeks 6 and 26 of PRECiSE 2, the mean (SD) QALYs were 0.4976 (0.2047) in the CZP group versus 0.4286 (0.2171) in the three injection followed by placebo group. A statistically significant gain in QALYs with CZP was observed in both trials: PRECiSE 1 0.0659 (p=0.001); PRECiSE 2 0.0690 (p=0.015). CONCLUSION: CZP improved both quality and quantity of remission and response period, as measured by QALYs, significantly more than placebo among patients with CD in two 26-week maintenance trials.