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Quantifying uncertainty in long-term care costs following introduction of new drug therapy: the importance of model choice Paul McNamee, Alessandra Vanoli, Debbie Hutchings, Ian McKeith, John Bond In the next 25 minutes... • Aims, methods and results of the paper • Conclusions and points for discussion Aims of the paper • To compare two approaches in modelling the net NHS costs of drug treatment for Alzheimer’s Disease • Application of deterministic and probabilistic modelling methods to estimate costs and explore uncertainty about likely “budget impact” to the NHS over 10 years • Apply these methods to 3 different policies (ALL, NG1, NG2) Some background • AD affects a large and growing number of older people • Drugs are effective at slowing disease progression • Uncertainty over whether they are ‘cost-effective’ • NICE recommends assessment of “budget impact” for NHS, but only partially done for AD drugs in 2001 • Recent guidance (March 05) - treatment should no longer be prescribed for new patients Methods -1 • Simulate cost impact for AD population (England and Wales) – ONS population data – MRC ageing study for AD prevalence rates – Systematic review of effects of treatment on cognition – Long term prognosis from observational studies • OLS and GLM regression models estimate cost effect of changes in disease progression Methods – 2 Regression models Ordinary least squares (OLS) • Identity link • Normal (Gaussian) distribution Generalized Linear Model (GLM) • Log link • Gamma or Negative Binomial Distribution N=371 dependent variable: weekly cost Constant term allowed. independent variables: sex, age, ADL, MMSE Estimated incremental cost impact over 10 yrs 2002/03 prices £m method Deterministic based on OLS pop. estimates ALL 550 NG1 NG2 drugs 851 115 drugs 233 298 drugs 449 With extra clinic visits NICE 2001 794 N/A 182 Drugs 42 pa 427 N/A Estimated incremental 10 yr cost per patient 2002/03 prices £ (% diff from OLS estimate) method OLS det OLS prob GLM det GLM prob pop. All cohort 1792 1810 2107 (+18) 1608 (-11) NG1 597 607 736 (+23) 334 (-45) NG2 1550 1591 1785 (+15) 1389 (-13) Conclusions • Drug treatment for AD likely to lead to additional costs to the NHS • Choice of modelling method makes a difference to magnitude of estimates Discussion points • A GLM framework for probabilistic analysis more likely to produce outliers • Lack of evidence on long term effects • Estimates based on 10 year old observations of costs of care • Estimates assume full adoption for different NICE policy decisions – but how realistic? • How important is the “budget impact” question to local and national decisionmakers?