response to the initial therapy or response is lost during
maintenance therapy; (C) '5 mg/kg and 10 mg/kg infliximab
+ adalimumab': initial therapy using 5 mg/kg infliximab,
if there is no response, dose escalated to 10 mg/kg
infliximab, and if response is lost during maintenance
therapy, switch to adalimumab. Details on strategy B and
C are shown in Figure 1.
Markov model
A five-health state Markov model was constructed to compare
the incremental cost-utility of these three management
strategies. The Active Ulcerative Colitis Trials 1 and
2 (ACT 1 and ACT 2) were the main sources of the clinical
parameters used in the model[10]. The length of a Markov
cycle was determined by the treatment intervals adopted
in the ACTstudies.
Specifically, the first cycle was from week 0 to week 8, the
second from week 9 to week 30, the third from week 31 to
week 54, and then every 27 weeks for each cycle starting
from week 55. Remission was defined as a total Mayo
score of 2 points or lower, without individual sub-scores
exceeding 1 point[10]. As the definitions of remission and
response were overlapping in the ACT studies[10],
responders defined in the present study excluded those
achieving remission in order to make these two states