Abstract
Objective
To develop a function for mapping the eight-item Parkinson’s Disease Questionnaire (PDQ-8) to the EuroQol Group’s EQ-5D utility index.
Methods
Data from two surveys of 324 patients with Parkinson’s disease was divided into two groups. One was used to estimate the mapping functions by regression methods and the other was used to validate the mapping functions.
Results
A regression model with a non-linear trend explained 55% of the variation in EQ-5D utility values and had a mean absolute deviation (MAD) of 0.083. A regression model assuming a linear trend explained 52% of the variation and had an MAD of 0.085. In the validation sample, predicted values based on the aforementioned models respectively explained 42 and 44% of the variation in the observed EQ-5D utility values and both had MADs of about 0.1. The confidence intervals of the mean difference between these predicted values and the observed values totally fell within the pre-defined equivalence margin of 0.03 points. These predicted values were also similar to the observed EQ-5D utility values in terms of their association with clinical variables.
Conclusion
At the group level, but not at the individual level, the mapping functions can accurately map the PDQ-8 outcomes to the EQ-5D utility index.
Similar content being viewed by others
Abbreviations
- PDQ:
-
Parkinson’s disease questionnaire
- OLS:
-
Ordinary least squares
- CLAD:
-
Censored least absolute deviation
References
Gold, M. R., Patrick, D. L., Torrance, G. W., Fryback, D. G., Hadorn, D. C., Kamlet, M. S., et al. (1996). Identifying and valuing outcomes. In M. R. Gold, J. E. Siegel, L. B. Russell & M. C. Weinstein (Eds.), Cost-effectiveness in health and medicine (pp. 82–134). New York, NY: Oxford University Press.
Drummond, M. F., O’Brien, B. J., Stoddart, G. L., & Torrance, G. W. (1997) Cost-utility analysis. In M. F. Drummond, B. J. O’Brien, G. L. Stoddart & G. W. Torrance (Eds.), Methods for the economic evaluation of health care programmes (2nd ed.). Oxford: Oxford University Press, pp. 139–199.
Rabin, R., & de Charro, F. (2001). EQ-5D: a measure of health status from the EuroQol Group. Annals of Medicine, 33, 337–343. doi:10.3109/07853890109002087.
Horsman, J., Furlong, W., Feeny, D., & Torrance, G. (2003). The Health Utilities Index (HUI): concepts, measurement properties and applications. Health and Quality of Life Outcomes, 1, 54. doi:10.1186/1477-7525-1-54.
Lawrence, W. F., & Fleishman, J. A. (2004). Predicting EuroQoL EQ-5D preference scores from the SF-12 Health Survey in a nationally representative sample. Medical Decision Making, 24, 160–169. doi:10.1177/0272989X04264015.
Sullivan, P. W., & Ghushchyan, V. (2006). Mapping the EQ-5D index from the SF-12: US general population preferences in a nationally representative sample. Medical Decision Making, 26, 401–409. doi:10.1177/0272989X06290496.
Brennan, D. S., & Spencer, A. J. (2006). Mapping oral health related quality of life to generic health state values. BMC Health Services Research, 6, 96. doi:10.1186/1472-6963-6-96.
Wu, E. Q., Mulani, P., Farrell, M. H., & Sleep, D. (2007). Mapping FACT-P and EORTC QLQ-C30 to patient health status measured by EQ-5D in metastatic hormone-refractory prostate cancer patients. Value in Health, 10, 408–414. doi:10.1111/j.1524-4733.2007.00195.x.
Brooks, R., Rabin, R., & de Charro, F (Eds.). (2003). The measurement and valuation of health status using EQ-5D: a European perspective. Dordrecht: Kluwer Academic Publications.
Dolan, P. (1997). Modeling valuations for EuroQol health states. Medical Care, 35, 1095–1108. doi:10.1097/00005650-199711000-00002.
Tsuchiya, A., Ikeda, S., Ikegami, N., Nishimura, S., Sakai, I., Fukuda, T., et al. (2002). Estimating an EQ-5D population value set: the case of Japan. Health Economics, 11, 341–353. doi:10.1002/hec.673.
Jenkinson, C., Fitzpatrick, R., Peto, V., Greenhall, R., & Hyman, N. (1997). The PDQ-8: development and validation of a short-form Parkinson’s disease questionnaire. Psychology & Health, 12, 805–814. doi:10.1080/08870449708406741.
Marinus, J., Ramaker, C., van Hilten, J. J., & Stiggelbout, A. M. (2002). Health related quality of life in Parkinson’s disease: a systematic review of disease specific instruments. Journal of Neurology, Neurosurgery, and Psychiatry, 72, 241–248. doi:10.1136/jnnp.72.2.241.
Schrag, A., Selai, C., Jahanshahi, M., & Quinn, N. P. (2000). The EQ-5D—a generic quality of life measure—is a useful instrument to measure quality of life in patients with Parkinson’s disease. Journal of Neurology, Neurosurgery, and Psychiatry, 69, 67–73. doi:10.1136/jnnp.69.1.67.
Siderowf, A., Ravina, B., & Glick, H. A. (2002). Preference-based quality-of-life in patients with Parkinson’s disease. Neurology, 59, 103–108.
Tan, L. C. S., Luo, N., Nazri, M., Li, S. C., & Thumboo, J. (2004). Validity and reliability of the PDQ-39 and the PDQ-8 in English-speaking Parkinson’s disease patients in Singapore. Parkinsonism & Related Disorders, 10, 493–499. doi:10.1016/j.parkreldis.2004.05.007.
Luo, N., Tan, L. C. S., Li, S. C., Soh, L. K., & Thumboo, J. (2005). Validity and reliability of the Chinese (Singapore) version of the Parkinson’s disease questionnaire (PDQ-39). Quality of Life Research, 14, 273–279.
Tan, L. C., Lau, P. N., Au, W. L., & Luo, N. (2007). Validation of PDQ-8 as an independent instrument in English and Chinese. Journal of the Neurological Sciences, 255, 77–80. doi:10.1016/j.jns.2007.01.072.
Jenkinson, C., & Fitzpatrick, R. (2007). Cross-cultural evaluation of the short form 8-item Parkinson’s Disease Questionnaire (PDQ-8): results from America, Canada, Japan, Italy and Spain. Parkinsonism & Related Disorders, 13, 22–28. doi:10.1016/j.parkreldis.2006.06.006.
Luo, N., Chew, L. H., Fong, K. Y., Koh, D. R., Ng, S. C., Yoon, K. H., et al. (2003). Validity and reliability of the EQ-5D self-report questionnaire in English-speaking Asian patients with rheumatic diseases in Singapore. Quality of Life Research, 12, 87–92. doi:10.1023/A:1022063721237.
Luo, N., Chew, L. H., Fong, K. Y., Koh, D. R., Ng, S. C., Yoon, K. H., et al (2003). Validity and reliability of the EQ-5D self-report questionnaire in Chinese-speaking patients with rheumatic diseases in Singapore. Annals of the Academy of Medicine, Singapore, 32, 685–690.
Cheung, Y. B., Thumboo, J., Goh, C., Khoo, K. S., Che, W., & Wee, J. (2004). The equivalence and difference between the English and Chinese versions of two major, cancer-specific, health-related quality-of-life questionnaires. Cancer, 101, 2874–2880. doi:10.1002/cncr.20681.
Greene, W. H. (2003). Econometric analysis (5th ed.). Upper Saddle River, NJ: Prentice Hall.
Jolliffe, D., Krushelnytskyy, B., & Semykina, A. (2001). Censored least absolute deviations estimator. Stata Technical Bulletin, 10, 240–244.
Machin, D., Campbell, M., Fayers, P. M., & Pinol, A. P. Y. (1997). Sample size tables for clinical studies (2nd ed.). Oxford: Blackwell.
Dobrez, D., Cella, D., Pickard, A. S., Lai, J. S., & Nickolov, A. (2007). Estimation of patient preference-based utility weights from the functional assessment of cancer therapy—general. Value in Health, 10, 266–272. doi:10.1111/j.1524-4733.2007.00181.x.
Cheung, Y. B., Wong, L. C., Tay, M. H., Toh, C. K., Koo, W. H., Epstein, R., et al. (2004). Order effects in the assessment of quality of life in cancer patients. Quality of Life Research, 13, 1217–1223. doi:10.1023/B:QURE.0000037499.80080.07.
Kemmler, G., Holzner, B., Kopp, M., Dünser, M., Margreiter, R., Greil, R., et al. (1999). Comparison of two quality-of-life instruments for cancer patients: the Functional Assessment of Cancer Therapy—General and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-C30. Journal of Clinical Oncology, 17, 2932–2940.
Luo, N., Chew, L. H., Fong, K. Y., Koh, D. R., Ng, S. C., Yoon, K. H., et al. (2003). Do English and Chinese EQ-5D versions demonstrate measurement equivalence? An exploratory study. Health and Quality of Life Outcomes, 1, 7. doi:10.1186/1477-7525-1-7.
Sengupta, N., Nichol, M. B., Wu, J., & Globe, D. (2004). Mapping the SF-12 to the HUI3 and VAS in a managed care population. Medical Care, 42, 927–937. doi:10.1097/01.mlr.0000135812.52570.42.
Acknowledgments
The authors would like to thank the EuroQol Group (http://www.euroqol.org/) and the Health Services Research Unit (Oxford University) for allowing us to use their instruments in this study.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Cheung, Y.B., Tan, L.C.S., Lau, P.N. et al. Mapping the eight-item Parkinson’s Disease Questionnaire (PDQ-8) to the EQ-5D utility index. Qual Life Res 17, 1173–1181 (2008). https://doi.org/10.1007/s11136-008-9392-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11136-008-9392-8