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Monday, 24 October 2005 - 3:45 PM

EXPECTED VALUE OF RESEARCH ON INTERVENTIONS TO INCREASE UPTAKE TO BREAST CANCER SCREENING

Nicky J. Welton, PhD, Bristol University, Bristol, United Kingdom and A. E. Ades, PhD, Medical Research Council, Bristol, United Kingdom.

Purpose: To develop methods to assess the value of further research into interventions to increase uptake to breast cancer screening in the UK: 1) before a cluster randomised trial reported in 2001 and 2) after that trial.

Methods: We analysed data from a cluster randomised 2x2 factorial trial on letter and flag interventions to increase attendance at breast cancer screening in the UK (Bankhead et al 2001). We use a random effects logistic regression model in a Bayesian decision analytic framework, which allows reasonable estimation of the interaction term, and is embedded directly into a cost-effectiveness model incorporating costs and life-years saved by screening and early treatment. We consider how to calculate the expected value of a trial of this design 1) before the trial and 2) after the trial. Prior to the 2001 study there was a substantial body of research into various types of intervention (mainly from Australia and the US). We use this evidence to inform a multivariate normal prior for our regression coefficients, including correlations. We then combine this prior information with the data to obtain a multivariate normal posterior that becomes the prior after the trial. We calculate, for both priors, the expected value of removing some uncertainty in intervention efficacy parameters by running a future cluster randomised factorial design trial of given cluster size - Expected Value of Sample Information (EVSI). EVSI is calculated by simulating future data from the prior and using weighted least-squares regression to obtain multivariate normal sufficient statistics for the regression coefficients, including correlations.

Results: Using a £30,000 valuation of a QALY, EVSI per woman invited to screening was £2.88 before and £1.58 after the trial, for the 2001 trial study design. Population EVSI over a 10-year horizon was £6.7m before and £3.6m after the trial.

Conclusions: By making multivariate normal approximations, we have calculated EVSI for cluster-randomised trials. There was considerable value in running the 2001 trial, and although the 2001 trial has reduced decision uncertainty, there is still value in running a similar trial in the future. We discuss methods for finding the optimal cluster sizes for a future study, allowing for the cost of the study and the opportunity cost of receiving a sub-optimal intervention during the trial.


See more of Oral Concurrent Session N - Health Economics
See more of The 27th Annual Meeting of the Society for Medical Decision Making (October 21-24, 2005)