Developing a health state classification system from NEWQOL for epilepsy using classical psychometric techniques and Rasch analysis: a technical report

Mulhern, B and Rowen, D and Brazier, J and Jacoby, A and Marson, T and Snape, D and Hughes, D and Latimer, N and Baker, GA (2010): Developing a health state classification system from NEWQOL for epilepsy using classical psychometric techniques and Rasch analysis: a technical report.

Abstract

Aims: Resource allocation amongst competing health care interventions is informed by evidence of both clinical- and cost-effectiveness. Cost-utility analysis is increasingly used to assess cost effectiveness through the use of Quality Adjusted Life Years (QALYs). This requires health state values. Generic measures of health related quality of life (HRQL) are usually used to produce these values, but there are concerns about their relevance and sensitivity in epilepsy. This study develops a health state classification system for epilepsy from the NEWQOL battery, a validated questionnaire measuring QoL in epilepsy. The classification system will be amenable to valuation for calculating QALYs.

Methods: Factor and other psychometric analyses were undertaken to investigate the factor structure of the battery, and assess the validity and responsiveness of the items. These analyses were used alongside Rasch analysis to select the dimensions included in the classification system, and the items used to represent each domain. Analysis was carried out on a trial dataset of patients with epilepsy (n=1611). Rasch and factor analysis were performed on one half of the sample and validated on the remaining half. Dimensions and items were selected that performed well across all analyses.

Results: The battery was found to demonstrate reliability and validity but responsiveness across time periods for many of the items was low. A six dimension classification system was developed: worry about seizures, depression, memory, cognition, stigmatism and control, each with four response levels.

Conclusions: It is feasible to develop a health state classification system from a battery of instruments using a combination of classical psychometric, factor and Rasch analysis. This is the first condition-specific health state classification developed for epilepsy and the next stage will produce preference weights to enable the measure to be used in cost-utility analysis.

• 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; epilepsy
• 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

Abetz L, Jacoby A, Baker GA, McNulty P (2000). Patient-based assessments of quality of life in newly diagnosed epilepsy patients: validation of the NEWQOL. Epilepsia 41(9):1119-28.

Aldenkamp AP, Baker GA (1997). The Neurotoxicity Scale II: results of a patient-based scale assessing neurotoxicity in patients with epilepsy. Epilepsy Research 27:165-73.

Baker GA, Jacoby A, Francis P, Chadwick DW (1995). The Liverpool adverse drug events profile. Epilepsia 36:S59.

Birbeck GL, Hays RD, Cui XP, et al (2002). Seizure reduction and quality of life improvements in people with epilepsy. Epilepsia 43(5):535–8.

Bjelland I, Dahl AA, Haug TT, Neckelmann D (2002). The validity of the Hospital Anxiety and Depression Scale – An updated literature review. Journal of Psychosomatic Research 52(2):69-77.

Brazier J, Czoski-Murray C, Roberts J, Brown MC, Symonds S, Kelleher C (2008). Estimation of a preference-based index from a condition specific measure: The King's Health Questionnaire. Medical Decision Making 28(1):113-26.

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.

Brazier JE, Rowen D, Tsuchiya A, Yang Y, Young T (2010). What a pain: adding a generic dimension to a condition-specific preference-based measure. Health Economics Study Group, Cork, June 2010.

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

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

Ettinger A, Reed M, Cramer J (2004). Depression and comorbidity in community-based patients with epilepsy or asthma. Neurology 63(6):1008–14.

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

Jacoby A (1992). Epilepsy and the quality of everyday life: findings from a study of people with well-controlled epilepsy. Social Science Medicine 34(6):657–66.

Jacoby A, Johnson AL, Chadwick DW (1992). Psychosocial outcomes of antiepileptic drug discontinuation. Epilepsia 33:123-31.

Jacoby A, Baker GA, Smith DF, et al (1993). Measuring the impact of epilepsy: the development of a novel scale. Epilepsy Research 16:83-8.

Jacoby A (1994). Felt versus enacted stigma: a concept revisited: evidence from a study of people with epilepsy in remission. Social Science Medicine 38:269-74.

Jacoby A, Baker GA, Steen N, et al (1996). The clinical course of epilepsy and its psychosocial correlates: findings from a UK community study. Epilepsia 37:148-61.

Jacoby A, Baker GA (2008). Quality of life trajectories in epilepsy: A review of the literature. Epilepsy and Behavior 12(4):557-71.

Jacoby A, Snape D, Baker GA (2009). Determinants of quality of life in people with epilepsy. Neurologic Clinics 27(4):843-63.

Linacre JM (1999). Investigating rating scale category utility. Journal of Outcome Measurement 3(2):103-122.

Loring DW, Meador KJ, Lee GP (2004). Determinants of quality of life in epilepsy. Epilepsy and Behaviour 5(6):976–80.

Marson AG, Appleton R, Baker GA, Chadwick DW, Doughty J, Eaton B, Gamble C, Jacoby A, Shackley Smith DF, Smith PEM, Smith CT, Tudur-Smith C, Vanoli A, Williamson PR (2007). A randomised controlled trial examining the longer-term outcomes of standard versus new antiepileptic drugs. The SANAD trial. Health Technology Assessment 11(37).

Marson AG, Al-Kharusi AM, Alwaidh M, Appleton R, Baker GA, Chadwick DW, Cramp C, Cockerell OC, Cooper PN, Doughty J, Eaton B, Gamble C, Goulding PJ, Howell SJL, Hughes A, Jackson M, Jacoby A, Kellett M, Lawson GR, Leach JP, Nicolaides P, Roberts R, Shackley P, Shen J, Smith DF, Smith PEM, Smith CT, Tudur-Smith C, Vanoli A, Williamson PR (2007). The SANAD study of effectiveness of carbamazepine, gabapentin, lamotrigine, oxcarbazeprine, or topiramate for treatment of partial epilepsy: an unblended randomised controlled trial. Lancet 369:1000-15.

Mensah SA, Beavis JM, Thapar AK, Keer MP (2007). A community study of the presence of anxiety disorder in people with epilepsy. Epilepsy and Behaviour 11:118-24.

Mulhern B, Smith SC, Rowen D, Brazier J, Knapp M, Lamping DL, Loftus V, Young TA, Howard RJ, Banerjee S (2010). Improving the measurement of QALYs in dementia: Developing patient- and carer-reported health state classification systems using Rasch analysis. HEDS Discussion Paper 10/13.

National Health Service (2008). Epilepsy – Introduction. http://www.nhs.uk/epilepsy. Accessed 09/08/2010.

National Institute for Health and Clinical Excellence (2008). Guide to the methods of technology appraisal. London: National Institute for Health and Clinical Excellence.

Pearlin L, Schooler C (1978). The structure of coping. Journal of Health and Social Behaviour 19:2-21.

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

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

Selai CE, Elstner K, Trimble MR (2000). Quality of life pre and post epilepsy surgery. Epilepsy Research 38:67-74.

SPSS for windows. (2007). Release 16.0. Chicago: SPSS Inc.

Stavem K, Bjornaes H, Lossius MI (2001). Properties of the 15D and EQ-5D utility measures in a community sample of people with epilepsy. Epilepsy Research 44:179-89.

Suurmeijer TPBM, Reuvekamp MF, Aldenkamp BP (2001). Social functioning, psychological functioning, and quality of life in epilepsy. Epilepsia 42(9):1160–8.

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.

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

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.

Young T, Yang Y, Brazier JE, Tsuchiya A, Coyne K (2009). The first stage of developing preference-based measures: constructing a health-state classification using Rasch analysis. Quality of Life Research 18(2):253-65.

Young T, Rowen D, Norquist J, Brazier J (2010). Developing preference-based health measures: using Rasch analysis to generate health state values. Quality of Life Research 19(6):907-17.

Young TA, Yang Y, Brazier JE, Tsuchiya A (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. Medical Decision Making, early view.

Zeber JE, Copeland LA, Amuan M, et al (2007). The role of comorbid psychiatric conditions in health status in epilepsy. Epilepsy and Behaviour 10(4):539–46.

Zigmond AS, Snaith RP (1983). The Hospital Anxiety and Depression Scale. Acta Psychiatrica Scandinavica 67:361-70.