Analytical approach:
A decision analytic model was used to assess the costs and outcomes of the two interventions. The lifetime of the mother was the time horizon and the authors reported that a societal perspective was adopted.
Effectiveness data:
The baseline efficacy of antibiotic prophylaxis during labour, the probabilities for each strategy, and the outcomes were derived from a systematic review of the literature, including a search of the references of identified relevant articles. The authors searched PubMed, Scopus, the Cochrane Library, the Centers for Disease Control and Prevention's guidelines, and the Internet, using Knowledge Finder, for reports from 1966 to January 2009. The search strategy was reported. The main effectiveness parameter was the probability of the recurrence of group B streptococci colonisation.
Monetary benefit and utility valuations:
The utilities were taken from published sources.
Measure of benefit:
The measure of benefit was quality-adjusted life-years (QALYs) gained. As these outcomes could be generated over the lifetime of the patient, future benefits were discounted at an annual rate of 3%.
Cost data:
The costs included those associated with screening, intrapartum antibiotic prophylaxis, treatment for maternal anaphylaxis and death, evaluation of newborns whose mother received antibiotic prophylaxis, and treatment of term neonatal early-onset group B streptococcal sepsis. The cost data were derived from a variety of published studies and fee schedules from government-sponsored insurance companies. All costs were inflated to 2008 prices and reported in US dollars ($). As they could be incurred over the lifetime of the patient, future costs were discounted at an annual rate of 3%.
Analysis of uncertainty:
A series of one-way sensitivity analyses was undertaken by varying the values of all the model parameters.