Strengths and limitations
The main strength of this study is that we compared app-based treatment
with care-as-usual. The pragmatic design is considered the gold standard
for economic evaluations in health care.24 Other
strengths are the inclusion of all common UI types, the use of
patient-centred and validated outcome measures, the 12-month follow-up
period, and the inclusion of sensitivity analyses to confirm the
robustness of our data.
The cost and effect analyses were sufficient to make valid conclusions
about cost-effectiveness. Although the ICER and ICUR are typically used
to represent costs associated with 1 unit of health gain, we set the
difference to focus on cost rather than health gains given that the
latter was comparable between the groups. Consideration of this health
gain would be confusing, as the minimal differences result in high
ratios of ICER and ICUR.
Limitations that must be considered are power and loss to follow-up.
Often, cost-effectiveness studies are underpowered because their power
depends on the primary outcome measure of a trial. This trial was
powered on non-inferiority of effectiveness after 4 months. In this
secondary analysis, 172 women (65.6%) were available for follow-up and
power was lower. By performing a bootstrap analysis, this issue does not
affect the results of the cost-effectiveness analysis. However, the
lower power must be considered in our effectiveness and subgroup
analyses. Loss to follow-up was associated with higher body mass index.
Participation of these women could have further improved effects and
lowered costs for both treatment groups, as weight loss is effective for
UI and a cheap intervention.