Developing an algorithm to convert routine measures of vision into utility values for glaucoma

Alavi, Y., Jofre-Bonet, M., Bunce, C. V., Wormald, R., Viswanathan, A., Foster, A. & Hitchings, R. (2011). Developing an algorithm to convert routine measures of vision into utility values for glaucoma. Ophthalmic Epidemiology, 18(5), pp. 233-243. doi: 10.3109/09286586.2011.602577

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Abstract

Purpose: Measures of quality of life called utility values (UVs) are needed to deliver the most cost-effective health care for glaucoma patients. UVs are rarely measured in clinical research and practice whereas clinical outcomes such as visual field are routinely collected. The aim was to develop an algorithm that calculates UVs directly from combinations of routine measures of binocular visual field, visual acuity, and contrast sensitivity.

Methods: A total of 132 outpatients with primary open angle glaucoma were recruited. The Time Trade-off (TTO) question was administered during face-to-face interviews. Binocular ETDRS logMAR visual acuity (VAB), binocular Pelli-Robson contrast sensitivity (CSB), and Humphrey 24-2 monocular visual field tests were performed on the same day. Integrated (binocular) visual field (IVF) scores were derived. Tobit regression analyses were used to model utility values based on combinations of IVF, VAB, CSB and other controlling factors.

Results: UVs recorded for 123 cases correlated significantly with both clinical measures of binocular visual function (r = -0.47, IVF; r = -0.48, VAB; r = 0.50, CSB; P <0.0001) and measures of vision-specific quality of life (r = 0.54-0.6, P <0.0001). Two final models incorporate terms for IVF and VAB, with or without living arrangements, and explain 24% and 31% of variation in utilities. CSB was not included in either model due to co-linearity between CSB and VAB confounding the models.

Conclusion: The models provide preliminary algorithms for predicting the expected UVs for glaucoma populations directly from clinical outcomes collected routinely in clinical practice. The predictions have limitations and further work is needed to improve these models.

Item Type: Article
Additional Information: Copyright Informa Healthcare, 2011.
Uncontrolled Keywords: Glaucoma, Quality of life, Utility values, Time trade-off, Cost-utility
Subjects: H Social Sciences > HB Economic Theory
Q Science > QA Mathematics > QA75 Electronic computers. Computer science
R Medicine > RE Ophthalmology
Divisions: School of Social Sciences > Department of Economics
URI: http://openaccess.city.ac.uk/id/eprint/3928

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