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Cost-utility analysis of the cochlear implant in children |
Cheng A K, Rubin H R, Powe N R, Mellon N K, Francis H W, Niparko J K |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Cochlear implants in profoundly deaf children.
Study population The study included profoundly deaf children each of who had received or were to receive a cochlear implant. Average hearing loss was greater than 90 dB for both ears.
Setting Hearing clinic at a hospital. The economic analysis was carried out in the USA.
Dates to which data relate Effectiveness and resource use data corresponded to the period between July 1998 and May 2000. The price year was 1999.
Source of effectiveness data The evidence for the final outcomes was based on a single study.
Link between effectiveness and cost data Costing was retrospectively performed and appears to have been based on the costs for the typical resources used in the context in question.
Study sample Power calculations were not used to determine the sample size. The study participants were parents of 78 profoundly deaf children (average age, 7.5 years) each of whom had received or would receive a cochlear implant. A total of 78 participants (with a mean (SD) child age of 7.5 (4.5) years) completed visual analog scale (VAS) versus subgroups that also completed the time-trade-off (TTO) (n=40) (with a mean (SD) child age of 7.4 (5.3) years) or the Health Utility Index (HUI) (n=22) (with a mean (SD) child age of 10 (4.9) years). Response rates were 74% (78 of 105) of eligible families for the VAS, 77% (40 of 52 for the TTO, and 73% (22 of 30) for the HUI. The number of families surveyed from the cohort of cochlear implant candidates was 48 for VAS, 32 for TTO, and 12 for HUI.
Study design This was a before and after study using cross-sectional surveys carried out in a single centre. The duration of the follow-up was not clear, except for the fact that recipients had an average of 1.9 years of implant use. Loss to follow-up was not reported. Parents rated their child's health state at the time of the survey, and immediately before, and 1 year before implantation. The VAS questionnaire was mailed to parents of each child who received an implant at the study institution. The HUI, appropriate only for children aged 5 years or older, was mailed to families of school-aged children who responded to the VAS. The time-trade-off (TTO) was conducted as parental interviews during routine appointments, following standardised protocols with visual aids.
Analysis of effectiveness The principle (intention to treat or treatment completers only) used in the analysis of effectiveness was not explicitly specified. The health outcome measures were health utility scores using three different instruments (the changes in scores from pre-implantation to post-implantation score) of VAS, TTO, and HUI. Pre-implantation indicates surveys taken immediately before implantation. There was no significant difference in characteristics among the VAS, TTO, and HUI subgroups, nor between the recipient and candidate cohorts, in VAS scores or sociodemographic and audiological characteristics. Because of the possibility of recall bias in retrospective assessment of quality of life before the implantation, the authors also administered the instruments to parents of deaf children who were eligible but who had not received an implant. Parents rated their children's health state at the time of the survey and 1-year previously. There were also no significant differences between recipients whose parents participated in the study and those who did not. The authors also retested a small sample of patients to assess test-retest reliability. For those who completed multiple instruments, Pearson correlations were calculated. Mean group VAS scores were also transformed into TTO scores by a power function, as another means of evaluating the validity of the TTO assessments.
Effectiveness results The mean change in VAS score was 0.27, (95% CI: 0.22 - 0.32), from a pre-implantation score of 0.59 (0.53 to 0.64) to a post-implantation score of 0.86 (95% CI: 0.83 - 0.89).
The corresponding change in TTO score was 0.22, (95% CI: 0.15 - 0.28), from a pre-implantation score of 0.75, (95% CI: 0.67 - 0.83) to a post-implantation score of 0.97, (95% CI: 0.93 - 1.00).
The mean change in HUI score was 0.39, (95% CI: 0.31 - 0.46), from a pre-implantation score of 0.25, (95% CI: 0.16 - 0.34) to a post-implantation score of 0.64, (95% CI: 0.57 - 0.70).
The VAS, TTO, HUI scores at surveys for the families surveyed from the cohort of cochlear implant candidates were 0.63, 0.77, and 0.30, respectively.
Clinical conclusions This is the first cochlear implant study to use the TTO. The TTO elicited robust gains in utility, but the scores were consistent with transformed VAS scores using established power functions described in the literature.
Measure of benefits used in the economic analysis Quality-adjusted life-years (QALYs) gained using TTO, VAS, and HUI were the measures of benefit adopted. The measurement of life expectancy was based on life tables. It was assumed that the cochlear implant would not alter life expectancy and that the implant would be used for the remainder of life. Parents were used as proxies to elicit health state utilities for children with profound deafness. The health benefits were directly represented by the effectiveness measures, the two being essentially the same in this case.
Direct costs Costs were discounted at 3%. Some quantities were reported separately from the costs. Cost items were reported separately. Direct medical costs were estimated using the Medicare resource-based relative-value scale (RBRVS) for inpatients and outpatient preoperative, operative, and postoperative services covered by the Physician Fee Schedule, average Medicare blended payment for hospital costs, wholesale cost of the device, average cost per surgery of complications and device failure, processor upgrade costs, and patient-borne costs of warranty, loss or damage insurance, batteries, change in educational costs, and travel costs. The perspective adopted in the cost analysis was that of society. Change in educational costs was based on differences in school placement before and after receiving the implant as previously described in a paper published in 1999. The Consumer Price Index was used to inflate the cost data to the adopted price year. The price year was 1999.
Indirect Costs Indirect costs were discounted at 3%. Quantities were reported separately from the costs. Indirect cost items were reported separately. Indirect costs covered time off from work and change in future earnings. A weighted-average salary based on employment status and sex was used. Change in future earnings took into account differences in school placement and non-deaf and deaf employment rates and wages. The price year was 1999.
Sensitivity analysis A series of one-way sensitivity analyses was performed by varying relevant covariates.
Estimated benefits used in the economic analysis Average life expectancy was assumed to be 78 years. Gains in QALYs for the cochlear implant recipients were 8.03 in terms of VAS, 6.54 in terms of TTO, and 11.59 in terms of HUI. QALYs were discounted at 3%.
Cost results The discount rate was 3%. The lifetime direct medical costs of the implantation and associated services were $60,228. Combining all costs, cochlear implantation would save $53,198 per child at a 3% discount rate.
Synthesis of costs and benefits The direct cost per QALY gained was reported as the cost-utility ratio, resulting in values of $9,029 per QALY using the TTO, $7,500 per QALY using the VAS, and $5,197 per QALY using the HUI.
Authors' conclusions Cochlear implants in profoundly deaf children have a positive effect on quality of life at reasonable direct costs and appear to result in net savings to society.
CRD COMMENTARY - Selection of comparators The strategy of not using cochlear implants was regarded as the comparator. This allowed the active value of the intervention to be evaluated but poses some problems since there was no control group.
Validity of estimate of measure of effectiveness The internal validity of the effectiveness results is hampered by the possibility of selection, recall, and parental proxy biases. However, it was claimed that recall biases were unlikely to affect the study results because the recipient patients revisited the state of being deaf daily when the processor was removed or, when the battery power was exhausted and also because candidates similar in key characteristics generated prospective preoperative scores nearly identical to recipients' retrospective preoperative scores. There was no significant difference in characteristics among the VAS, TTO, and HUI subgroups, nor between the recipient and candidate cohorts, in VAS scores or sociodemographic and audiological characteristics. There were also no significant differences between recipients whose parents participated in the study and those who did not. The study sample appears to have been representative of the study populations.
Validity of estimate of measure of benefit The estimate of benefits was obtained directly from the effectiveness analysis. This choice of estimate was appropriate and justified.
Validity of estimate of costs Positive aspects of the cost analysis were as follows: most quantities were reported separately from the costs; cost items were reported separately; adequate details of methods of cost estimation were given; the price year and the perspective adopted in the cost analysis were reported; the effects of alternative procedures on indirect costs were addressed; and sensitivity analyses were performed on some resource use and cost data. A limitation of the cost analysis was that costing was not performed on the same patient sample as that used in the effectiveness analysis.
Other issues The authors' conclusion appears to be justified given the above caveats. The issue of generalisability to other settings or countries was addressed by performing sensitivity analysis and appropriate comparisons were made with other studies. The issue of whether the study sample was representative of the study population was addressed by acknowledging that the study patients represented deaf children who had received or would receive an implant at a large tertiary care centre. The study patients had higher socioeconomic status than the general population, but utilities were similar across strata of parent educational level.
Implications of the study Regarding the possibility of parental proxy bias, future longitudinal assessments that include self-reported ratings from the older children would be informative.
Source of funding Supported in part by a training grant from the National Institute on Deafness and Other Communication Disorders (Dr Cheng) and grants from the Deafness Research Foundation (Drs Cheng and Niparko), the Advisory Board Foundation (Drs Cheng and Niparko), and the Sidgmore Family Foundation (Drs Rubin and Niparko).
Bibliographic details Cheng A K, Rubin H R, Powe N R, Mellon N K, Francis H W, Niparko J K. Cost-utility analysis of the cochlear implant in children. JAMA 2000; 284(7): 850-856 Indexing Status Subject indexing assigned by NLM MeSH Child; Cochlear Implants /economics; Cost-Benefit Analysis; Cross-Sectional Studies; Deafness /therapy; Female; Health Care Costs /statistics & Humans; Male; Pain Measurement; Quality of Life; Quality-Adjusted Life Years; United States; numerical data AccessionNumber 22000008256 Date bibliographic record published 31/07/2001 Date abstract record published 31/07/2001 |
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