To adjust for baseline differences, characteristics of site and residents that differed
between the intervention groups at baseline were included in models as covariates.
The best method for presenting ICERs in this context is uncertain. Since the CMAI is
effectively a count variable, it was decided to present the cost per behaviour avoided
(i.e. a cost per 1-point reduction in one individual).
Since the analysis required a number of assumptions, in particular regarding the
amount of intervention-specific time spent by each member of staff, a univariate
sensitivity analysis was undertaken. This analysis investigated the effect of changing
the model parameters on the baseline conclusions. Thus, the estimated time spent on
DCM was increased and decreased by 8 hours per month to reflect uncertainty about
the actual time spent on activities related to mapping and devising the care plan. In
addition, the effects of increasing or decreasing the pharmacological costs by 20% in
each of the intervention arms sequentially were analysed.
The perspective employed was that of the health service. Thus, no costs accruing
beyond the residential home were considered. Discounting was not undertaken since
all outcomes and costs occurred in the first year. Whilst it may be of considerable
interest to ascertain whether benefits endured beyond the study period, no evidence
was available which allowed this to be estimated in this study.
Results and Discussion
The clinical outcomes will be reported fully elsewhere [14] . Briefly, levels of
agitation and aggression as measured by the CMAI decreased in residents enrolled in
both the PCC and DCM intervention arms compared to those in Usual Care (UC),
more so for PCC than for DCM. Greater variability in the PCC scores after evaluation
meant that it was not statistically significantly better than UC while DCM was. These
results are outlined in
Table 1. Even when corrected for the differing baseline characteristics, the significant
interaction term remained (p=0.001). (see Figure 2).