Analytical approach:
A decision tree was used to assess the impact of the test on costs; effectiveness was not modelled as no significant differences in effectiveness were identified by a systematic review. The time horizon was from hospital admission to the time of delivery. The authors stated that they took a UK NHS perspective.
Effectiveness data:
A systematic review was conducted for clinical effectiveness and test accuracy. Clinical effectiveness was measured by the impact of the test on the incidence of preterm births over different gestation periods, hospital admissions, administration of treatment, and newborn and maternal health outcomes. These outcomes were from five randomised controlled trials; test accuracy was from 54 diagnostic accuracy studies. Where three or more studies reported the same outcome, a random-effects model was used to pool their data. Based on the trials, it was assumed that testing did not lead to more adverse events or worse pregnancy outcomes than usual care.
Monetary benefit and utility valuations:
Not relevant.
Measure of benefit:
No benefit measure was used, as there was no evidence of a significant difference in effectiveness with the addition of the test.
Cost data:
The cost categories included the foetal fibronectin test, hospital admissions, and interventions. The cost of the test was from a Health Technology Assessment report, for an alternative form of the test. Admission and treatment rates were from the only identified UK study. Treatment costs were from the British National Formulary, and hospital costs were NHS reference costs. Emergency hospital transfer costs were from the Personal Social Services Research Unit. All costs were reported in 2011 UK £.
Analysis of uncertainty:
One-way sensitivity analyses were performed for all parameters. Probabilistic sensitivity analysis was undertaken to estimate the impact of joint parameter uncertainty on the results. Exploratory analysis assessed different prices for the foetal fibronectin test, varying from zero to £300. Scenario analyses tested various alternative assumptions.