Improving the measurement of QALYs in dementia: developing patient- and carer-reported health state classification systems using Rasch analysis

Mulhern, B and Smith, SC and Rowen, D and Brazier, JE and Knapp, M and Lamping, DL and Loftus, V and Young, Tracey A. and Howard, RJ and Banerjee, S (2010): Improving the measurement of QALYs in dementia: developing patient- and carer-reported health state classification systems using Rasch analysis.

Abstract

Objectives: Cost-utility analysis is increasingly used to inform resource allocation. This requires a means of valuing health states before and after intervention. Although generic measures are typically used to generate values, these do not perform well with people with dementia. We report the development of a health state classification system amenable to valuation for use in studies of dementia, derived from the DEMQOL system, a measure of health-related quality of life in dementia by patient self-report (DEMQOL) and carer proxy-report (DEMQOL-Proxy).

Methods: Factor analysis was used to determine the dimensional structure of DEMQOL and DEMQOL-Proxy. Rasch analysis was subsequently used to investigate item performance across factors in terms of item-level ordering, functioning across subgroups, model fit and severity-range coverage. This enabled the selection of one item from each factor for the classification system. A sample of people with a diagnosis of mild/moderate dementia (n=644) and a sample of carers of those with mild/moderate dementia (n=683) were used.

Results: Factor analysis found different 5-factor solutions for DEMQOL and DEMQOL-Proxy. Following item reduction and selection using Rasch analysis, a 5-dimension classification for DEMQOL and a 4-dimension classification for DEMQOL-Proxy were developed. Each item contained 4 health state levels.

Conclusion: Combining Rasch and classical psychometric analysis is a valid method of selecting items for dementia health state classifications from both the patient and carer perspectives. The next stage is to obtain preference weights so that the measure can be used in the economic evaluation of treatment, care and support arrangements for dementia.

• Item Type: MPRA Paper
• Language: English
• Keywords: quality adjusted life years; health related quality of life; Rasch analysis; preference-based measures of health; health states; dementia
• Subjects: I - Health, Education, and Welfare > I3 - Welfare, Well-Being, and Poverty > I31 - General Welfare, Well-Being; I - Health, Education, and Welfare > I1 - Health > I19 - Other

References

Brooks R (1996). EuroQol: The current state of play. Health Policy 37(1):53-72.

Dolan P (1997). Modeling valuations for EuroQol health states. Med Care 35(11):1095-108.

Brazier J, Roberts J, Deverill M (2002). The estimation of a preference-based measure of health from the SF-36. Journal of Health Economics 21(2):271-92.

Feeny D, Furlong W, Torrance GW, et al (2002). Multiattribute and single-attribute utility functions for the Health Utilities Index Mark 3 system. Med Care 40(2):113-28.

Drummond MF, Sculpher MJ, O’Brien BJ, et al (2005). Methods for the economic evaluation of health care programmes (3rd edn). Oxford: Oxford University Press.

Morris R, Morris L, Britton P (1988). Factors affecting the emotional wellbeing of the caregivers of dementia sufferers. B J Psychiatry 153:147-56.

Pickard L (2004). Caring for older people and employment. London School of Economics: Audit Commission and PSSRU.

Schneider J, Murray J, Banerjee S, Mann A (1999). EUROCARE: A cross-national study of co-resident spouse carers for people with Alzheimer’s disease: I. Factors associated with carer burden. Int J Geriatr Psychiatry 14:651-61.

Prince M, Jackson J (2009). World Alzheimer Report. Alzheimer Disease International.

Knapp M, Prince M, Albanese E, et al (2007). Dementia UK: The full report. London: Alzheimer's Society.

Comas-Herrera A, Wittenberg R, et al (2007). Cognitive impairment in older people: the implications for future demand for long-term care services and their costs. Int J Geriatr Psychiatry 22:1037-45.

Brazier J, Deverill M, Green C, et al (1999). A review of the use of health status measures in economic evaluation. Health Technol Assess 3(9):i-164.

Holland R, Smith RD, Harvey I, et al (2004). Assessing quality of life in the elderly: a direct comparison of the EQ-5D and AQoL. Health Econ 13(8):793-805.

Selai C (2001). Assessing quality of life in dementia. Med Care 39(8):753-5.

Wolfs CAG, Dirksen CD, Kessels A, et al (2007). Performance of the EQ-5D and the EQ-5D+C in elderly patients with cognitive impairments. Health and Quality of Life Outcomes 5.

Jonsson L, Andreasen N, Kilander L, et al (2006). Patient- and proxy-reported utility in Alzheimer disease using the EuroQoL. Alzheimer Dis Assoc Disord 20(1):49-55.

Kunz S (2010). Psychometric properties of the EQ-5D in a study of people with mild to moderate dementia. Qual Life Res 19(3):425-34.

Brazier J, Dixon S (1995). The use of condition specific outcome measures in economic appraisal. Health Econ 4(4):255-64.

Young T, Yang YL, Brazier JE, et al (2009). The first stage of developing preference-based measures: constructing a health-state classification using Rasch analysis. Qual Life Res 18(2):253-65.

Brazier J, Czoski-Murray C, Roberts J, et al (2008). Estimation of a preference-based index from a condition-specific measure: The King's Health Questionnaire. Med Decis Making 28(1):113-26.

Young T, Rowen D, Norquist J, et al (2010). Developing preference-based health measures: using Rasch analysis to generate health state values. Qual Life Res 19:907-17.

Young TA, Yang Y, Brazier JE, et al (2010). The use of Rasch analysis in reducing a large condition specific instrument for preference valuation: The case of moving from AQLQ to AQL-5D. Med Decis Making, early view.

Mavranezouli I, Brazier JE, Young M, Barkham M (2009). Using Rasch analysis to form plausible health states amenable to valuation: the development of CORE-6D from CORE-OM in order to elicit preferences for common mental health problems. Health Economics and Decision Science Discussion paper 09/09.

Yang Y, Brazier J, Tsuchiya A, Coyne K (2008). Estimating a preference based index from the Overactive Bladder questionnaire. Value in Health 12(1):159-66.

Rasch G (1960). Probabilistic models for some intelligence and attainment tests. Chicago: University of Chicago Press. Reprinted 1980.

Smith SC, Lamping DL, Banerjee S, et al (2005). Measurement of health-related quality of life for people with dementia: development of a new instrument (DEMQOL) and an evaluation of current methodology. Health Technol Assess 9(10):1-107.

Smith SC, Lamping DL, Banerjee S, et al (2007). Development of a new measure of health-related quality of life for people with dementia: DEMQOL. Psychol Med 37(5):737-46.

Tennant A, McKenna SP, Hagell P (2004). Application of Rasch analysis in the development and application of quality of life instruments. Value in Health 7(Suppl 1):S22-26.

Smith SC, Murray J, Banerjee S, et al (2005). What constitutes health-related quality of life in dementia? Development of a conceptual framework for people with dementia and their carers. Int J Geriatr Psychiatry 20(9):889-95.

Folstein MF, Folstein SE, Mchugh PR (1975). Mini-mental state - practical method for grading cognitive state of patients for clinicians. J Psychiatr Res 12(3):189-98.

Banerjee S, Willis R, Matthews D, et al (2007). Improving the quality of care for mild to moderate dementia: an evaluation of the Croydon Memory Service Model. Int J Geriatr Psychiatry 22(8):782-8.

SPSS for windows. Release 16.0. Chicago: SPSS Inc; 2007.

Rasch Unidimensional Measurement Models (RUMM) 2020©. RUMM Laboratory Pty Ltd; 1997-2004.

Ferguson E, Cox T (1993). Exploratory factor analysis: A user's guide. International Journal of Selection and Assessment 1(2):84-94.

Prado-Jean A, Couratier P, Druet-Cabanac M, et al (2010). Specific psychological and behavioural symptoms of depression in patients with dementia. Int J Geriatr Psychiatry, early view.

Steinberg M, Shao H, Zandi P, et al (2008). Point and 5-year period prevalence of neuropsychiatric symptoms in dementia: the Cache County Study. Int J Geriatr Psychiatry 23(2):170-7.

Novella JL, Jochum C, Jolly D, et al (2001). Agreement between patients' and proxies' reports of quality of life in Alzheimer's disease. Qual Life Res 10(5):443-52.

Boyer F, Novella JL, Morrone I, et al (2004). Agreement between dementia patient report and proxy reports using the Nottingham Health Profile. Int J Geriatr Psychiatry 19(11):1026-34.

Linacre JM (1999). Investigating rating scale category utility. J Outcome Meas 3(2):103-22.

Brazier JE, Ratcliffe J, Tsuchiya A, et al (2007). Measuring and valuing health for economic evaluation. Oxford: Oxford University Press.

Hays RD, Morales LS, Reise SP (2000). Item response theory and health outcomes measurement in the 21st century. Med Care 38(9):28-42.

Reise SP, Waller NG (2009). Item response theory and clinical measurement. Annual Review of Clinical Psychology 5:27-48.

Mungas D, Reed BR (2000). Application of item response theory for development of a global functioning measure of dementia with linear measurement properties. Stat Med 19(11-12):1631-44.

Coucill W, Bryan S, Bentham P, et al (2001). EQ-5D in patients with dementia - An investigation of inter-rater agreement. Med Care 39(8):760-71.

Banerjee S, Samsi K, Petrie CD, et al (2009). What do we know about quality of life in dementia? A review of the emerging evidence on the predictive and explanatory value of disease specific measures of health related quality of life in people with dementia. Int J Geriatr Psychiatry 24(1):15-24.

Jones R, Sheehan B, Phillips P, et al (2009). DOMINO-AD protocol: donepezil and memantine in moderate to severe Alzheimer’s disease – a multicentre RCT. Trials 10:57.

Torrance GW, Thomas W, Sackett D (1972). A utility maximization model for evaluation of health care programmes. Health Serv Res 7:118-33.