Analytical approach:
The economic evaluation was based on a Markov model that projected the natural history of PID for healthy women receiving their first screening at 18 years. The time horizon of the analysis was 4 years. The authors stated that a societal perspective was adopted.
Effectiveness data:
The authors did not describe a review of the literature, thus the primary studies might have been identified selectively. Disease progression was estimated from a prospective cohort study that followed young women for 4 years (the GYN Infection Follow-Through Study). Information on other sources was not given. In particular, no details were given on screening accuracy and adherence to the screening programme, which represent key clinical inputs. Some assumptions were also made.
Monetary benefit and utility valuations:
The utility values were derived from the literature, but no details of these studies were given.
Measure of benefit:
The summary benefit measure was the quality-adjusted life-years (QALYs). These were discounted at an annual rate of 3%. PID cases avoided, which represents a key output of the model, were also reported.
Cost data:
The categories of costs considered in the analysis were office visits, medications, and time lost for seeking or receiving care. The medical costs were derived from published studies, while the cost of time was based on hourly wage rates from the Bureau of Labor. Similarly, resource use was estimated on the basis of published evidence. Future costs were discounted at an annual rate of 3%. The price year was 2004 and the costs were in US dollars ($).
Analysis of uncertainty:
Univariate and multivariate sensitivity analyses were undertaken to identify the impact of variations in model inputs on the cost-effectiveness results. The authors might have defined the ranges of values used. Longer time horizons, as well as other possible PID risk distributions, were considered in alternative analyses.