title: Health economic evaluation of plasma oxysterol screening in the diagnosis of Niemann-Pick Type C disease among intellectually disabled using discrete event simulation.
abstract: BACKGROUND
  Recently a less invasive method of screening and diagnosing Niemann-Pick C (NP-C) disease has emerged. This approach involves the use of a metabolic screening test (oxysterol assay) instead of the current practice of clinical assessment of patients suspected of NP-C (review of medical history, family history and clinical examination for the signs and symptoms). Our objective is to compare costs and outcomes of plasma oxysterol screening versus current practice in diagnosis of NP-C disease among intellectually disabled (ID) patients using decision-analytic methods.
  
  
  METHODS
  A discrete event simulation model was conducted to follow ID patients through the diagnosis and treatment of NP-C, forecast the costs and effectiveness for a cohort of ID patients and compare the outcomes and costs in two different arms of the model: plasma oxysterol screening and routine diagnosis procedure (anno 2013) over 5 years of follow up. Data from published sources and clinical trials were used in simulation model. Unit costs and quality-adjusted life-years (QALYs) were discounted at a 3% annual rate in the base case analysis. Deterministic and probabilistic sensitivity analyses were conducted.
  
  
  RESULTS
  The outcomes of the base case model showed that using plasma oxysterol screening for diagnosis of NP-C disease among ID patients is a dominant strategy. It would result in lower total cost and would slightly improve patients' quality of life. The average amount of cost saving was $3642 CAD and the incremental QALYs per each individual ID patient in oxysterol screening arm versus current practice of diagnosis NP-C was 0.0022 QALYs. Results of sensitivity analysis demonstrated robustness of the outcomes over the wide range of changes in model inputs.
  
  
  CONCLUSIONS
  Whilst acknowledging the limitations of this study, we conclude that screening ID children and adolescents with oxysterol tests compared to current practice for the diagnosis of NP-C is a dominant strategy with clinical and economic benefits. The less costly, more sensitive and specific oxysterol test has potential to save costs to the healthcare system while improving patients' quality of life and may be considered as a routine tool in the NP-C diagnosis armamentarium for ID. Further research is needed to elucidate its effectiveness in patients presenting characteristics other than ID in childhood and adolescence.
authors.affiliation: Division of Biochemical Diseases, Department of Pediatrics, B.C. Children's Hospital, Canada; Treatable Intellectual Disability Endeavour in British Columbia(1), Canada; Child and Family Research Institute, Centre for Molecular Medicine & Therapeutics, Canada; University of British Columbia, Vancouver, Canada. Electronic address: cvankarnebeek@cw.bc.ca.
authors.forename: Clara D M
authors.initials: CD
authors.lastname: van Karnebeek
authors.affiliation: University of British Columbia, Vancouver, Canada; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada. Electronic address: timamoh@mail.ubc.ca.
authors.forename: Tima
authors.initials: T
authors.lastname: Mohammadi
authors.affiliation: University of British Columbia, Vancouver, Canada; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada. Electronic address: nicole_t@mail.ubc.ca.
authors.forename: Nicole
authors.initials: N
authors.lastname: Tsao
authors.affiliation: Treatable Intellectual Disability Endeavour in British Columbia(1), Canada; University of British Columbia, Vancouver, Canada; Department of Pathology & Laboratory Medicine, BC Children's & Women's Hospital, Canada. Electronic address: gsinclair@cw.bc.ca.
authors.forename: Graham
authors.initials: G
authors.lastname: Sinclair
authors.affiliation: University of British Columbia, Vancouver, Canada; Adult Metabolic Diseases Clinic, Vancouver General Hospital, Canada. Electronic address: sandra.sirrs@vch.ca.
authors.forename: Sandra
authors.initials: S
authors.lastname: Sirrs
authors.affiliation: Division of Biochemical Diseases, Department of Pediatrics, B.C. Children's Hospital, Canada; Treatable Intellectual Disability Endeavour in British Columbia(1), Canada; University of British Columbia, Vancouver, Canada. Electronic address: sstockler@cw.bc.ca.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Stockler
authors.affiliation: University of British Columbia, Vancouver, Canada; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada. Electronic address: carlo.marra@ubc.ca.
authors.forename: Carlo
authors.initials: C
authors.lastname: Marra
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003198:Computer Simulation; D003362:Cost-Benefit Analysis; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D008297:Male; D052556:Niemann-Pick Disease, Type C / Q000175:diagnosis*; D011788:Quality of Life; D019057:Quality-Adjusted Life Years; D013261:Sterols / Q000097:blood*
chemical_list: D013261:Sterols
keywords: Diagnosis; Filipin staining; Global developmental delay; Inborn error of metabolism; Intellectual disability; NPC1; NPC2; Oxysterol; Screening; Treatment