Verteporfin photodynamic therapy for neovascular age-related ...

DOI: 10.3310/hta16060Health Technology Assessment 2012; Vol. 16: No. 671for the extent of visual loss, that is BCVA. However, our data were obtained over relatively shortdurations of follow-up and it is possible that adaptation occurs only over longer periods of time.Narrative reviews have concluded that utility decreases with deteriorating visual function, 16,17,68but few studies have systematically quantified the relationships between these measures forpatients with nAMD (Table 22). 18,64 Our estimate of ~0.1 change in utility per 100 lettersis consistent with utility estimates based on the SF-6D or the EQ-5D. It is lower than theestimates based on the HUI3 64 (see below) and those based on preferences elicited directlyfrom patients. 18,65 The distributions of preferences elicited directly from AMD patients weremarkedly skewed in contrast to scores on preference-based utility measures derived fromsocietal valuations (acknowledging that this contrast is both between source of valuation, i.e.patients vs society, and between measure, i.e. directly elicited preference by time trade-off vspreference-based utility measure). This observation is consistent with some patients refusing totrade years of life for improved vision, 18,31 and raises concern about the validity of the method.More fundamentally, as generic measures of HRQoL are used to make broad comparisonsacross interventions in different disease areas, it is more appropriate to value health states withpreference weights from the general population rather than specific groups. 13Is the Short Form questionnaire-6 Dimensions an appropriatemeasure of generic health-related quality of life?A generic HRQoL measure chosen for comparing health gain across disease areas should have adescriptive system that covers all the important dimensions of health. The SF-6D, like the EQ-5D,has a descriptive system that purports to meet the World Health Organization definition ofhealth: ‘complete physical, mental and social well-being and not merely the absence of disease orinfirmity’. 69 Utilities measured using the SF-6D are similar to those measured using the EQ-5D. 70By contrast, the HUI3 is based on a narrower, ‘within the skin’ definition of health focusingon impairment and not on the social context of the impairment. 71 Thus, the HUI3 consists ofitems that tap self-reported functioning more directly than the EQ-5D and SF-6D. The HUI3 is,therefore, likely to be ‘more sensitive’ 71 to visual loss than the SF-6D. 64 However, the HUI3 hasbeen criticised for using this relatively narrow description of health. 9TABLE 22 Estimates of utility from different studiesStudyInstrument/methodusedSource of utilityvaluesVisual acuity and utility observationsBrown et al.,2000 18 Time trade-off Patients 20/20 to 20/400 (0.0–1.3 logMAR or 70letters ≈ utility 0.89 to 0.52 ≈ 0.47 differenceEspallargues et al., EQ-5D General population ≤ 0.3 to > 2.0 logMAR or 120 letters ≈ utility2005 64 0.75–0.63 ≈ 0.12 differenceEspallargues et al., SF-6D General population ≤ 0.3 to > 2.0 logMAR or 120 letters ≈ utility2005 64 0.70–0.63 ≈ 0.07 differenceEspallargues et al., HUI3 General population ≤ 0.3 to > 2.0 logMAR or 120 letters ≈ utility2005 64 0.50–0.10 ≈ 0.40 differenceEspallargues et al., Visual analogue2005 64 scalePatients≤ 0.3 to > 2.0 logMAR or 120 letters ≈ utility0.71–0.59 ≈ 0.12 differenceTime trade-off Patients ≤ 0.3 to > 2.0 logMAR or 120 letters ≈ utilityEspallargues et al.,0.222005 64 0.73–0.47 ≈ 0.26 differenceVPDT cohort study SF-6D General population Regression coefficient, 0.0012 per letter 0.120.1 logMAR, i.e. five letters.Approximate utilitychange per 100 letters0.670.100.060.330.10© Queen’s Printer and Controller of HMSO 2012. This work was produced by Reeves et al. under the terms of a commissioning contract issued by theSecretary of State for Health.