The analysis was based on a single study with a short time horizon. The authors stated that the analysis was carried out from the perspective of the health system, which was the UK National Health Service (NHS).
The clinical data came from a published randomised controlled trial (RCT), namely the Isosorbide MOnonitrate against Placebo (IMOP) trial, which involved 350 women at a single institution between March 2005 and December 2006. There were 177 women in the isosorbide mononitrate group and 173 women in the placebo group. Women were followed up until delivery or possible neonatal admission to special care. The key clinical outcome was the time interval from hospital admission to delivery.
Monetary benefit and utility valuations:
Measure of benefit:
The benefit measure was the reduction in the time between hospital admission and delivery, expressed in hours.
The economic analysis considered the costs of labour induction, labour procedures, and both maternal and neonatal complications, including medical and nursing staff, equipment, consumables, revenue and capital overheads, and drugs. The resource use data were collected alongside the RCT, using specific collection forms. The unit costs came from various sources, including the hospital finance department and Department of Health Reference Costs. All costs were in UK pounds sterling (£) and the price year was 2007. Conventional tools were used to test the statistical significance of the cost differences.
Analysis of uncertainty:
Non-parametric bootstrapping was used to generate confidence intervals (CIs) around the mean costs, benefits, and cost-effectiveness ratios. A sensitivity analysis was carried out on the occupancy rates for maternity care and the per day costs for both maternity and neonatal care. Alternative assumptions were based on the hospital database and the ranges of costs were from the Department of Health.