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.

Multichannel cochlear implant (MCCI) for profoundly deaf individuals.

Treatment.

Cost-utility analysis.

Profoundly deaf individuals.

Hospital. The economic study was carried out in Baltimore, MD, USA.

The effectiveness data were obtained from studies published in 1992 and 1993. The costing was mainly performed on 17 patients in the study site whose data were collected between July 1993 and June 1994. The fiscal year adopted in the study was 1993.

Effectiveness data were derived from a review of previously published studies, a survey study and expert opinion.

The costing was mainly performed on 17 patients who underwent implantation in the study site.

No power calculations were reported. The implanted group consisted of 301 patients randomly selected from a record of patients, whereas the pre-implant group (awaiting surgical placement of a cochlear implant) consisted of 38 individuals. A questionnaire consisting of the Ontario Health Utilities Index was sent to both groups. The response rate in the implanted group was 76% versus 84% in the pre-implant group.

A retrospective cohort study. The average duration of the use of implanted device was 4.6 years.

The main outcome measure used was the average health utility attributed to each health state (implanted and pre-implanted states). A questionnaire, consisting of the Ontario Health Utilities Index, addressing vision, hearing, speech, emotion, ambulation, dexterity, cognition, self-care, and pain was sent to both groups. The groups were shown to be comparable in terms of socio-economic and demographic features.

The incremental benefit in health utility due to the cochlear implant was 0.204 (p<0.0001).

It appears that the implant user group had, on average, significantly better speech, hearing, and cognitive function as well as a more favourable emotional status than the group of similar individuals who were awaiting the placement of the device.

A decision-analytic model was used to estimate the cost-utility of the alternative health technologies.

The literature review assessed device failure rate, minor complication rate, major complication rate, probability of audiologic suitability, probability of medical suitability, probability of favourable anatomy, probability of exit after a major complication, and probability of re-implantation after device failure.

Not stated.

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Three published studies and a study of "current implant protocol" at the Johns Hopkins Hospital.

Not stated.

Not reported.

The device failure rate was 3%; minor complication rate, 3%; major complication rate, 6%; probability of audiologic suitability, 70%; probability of medical suitability, 95%; probability of favourable anatomy, 98%; probability of exit after a major complication, 1%; and probability of re-implantation after device failure, 99%.

The authors also made assumptions about effectiveness.

It was assumed that patient life expectancy was 23 years.

The measure of benefits was quality adjusted life years (QALYs) gained using a decision-analytic model.

Costs were discounted. Quantities were not reported separately from the costs, although the cost items were reported separately. The costs measured were operational costs, costs of complications and follow up. The boundary adopted was the hospital. The expected cost of a major and a minor complication was extracted from a published paper. The prices used were from 1993.

Not considered.

US dollars ($).

A one way simple sensitivity analysis was performed on a wide range of cost and outcome parameters.

The cochlear implant resulted in an increase in health utility of 0.204. The corresponding QALYs were not reported. A life expectancy of 23 years was assumed. The discount rate was 5%.

A 5% discount rate was used. The cost results were:

total cost of preoperative evaluation was $1,915;

cost of surgery was $13,114;

initial device cost was $20,228;

cost of rehabilitation was $1,230;

cost of follow up was $7,157;

expected cost of a minor complication was $814;

expected cost of a major complication was $9,380.

The duration of costs was the expected lifetime of 23 years.

The synthesis measure used was the cost per QALY gained, using a 5% discount rate for both costs and benefits. The cost per QALY gained at 5% discount rate in 1993 dollars was $15,928, for the intervention. The final result was most sensitive to four parameters: the health utility increase with intervention, the length of implant use, and the device and surgical costs. The health utility outcome was the most sensitive parameter, with a decrease in the utility gain from 0.204 to 0.10 (-50%) resulting in a cost per QALY gained of $32,751 (+100%). An increase of the gain to 0.25 (+25%) resulted in a cost per QALY gained of $12,972 (- 18.75%).

Profound hearing loss has a significant effect on quality of life, and measurement of the changes that result from cochlear implant use indicates that this technology provides significant improvements and is quite cost-effective.

The reason for the choice of the comparator is clear.

The internal validity of the benefit results may be weakened by the study design adopted, and the apparent lack of a systematic literature review and quality assessment of primary studies included in the review.

The resource utilisation was not reported. Adequate details of methods of cost estimation were not given. The internal validity of the cost results may not be assured since the costing was not undertaken on the same patient sample as that used in the effectiveness analysis.

Given the lack of randomisation, sensitivity analysis, and statistical analysis of the costs, the results need to be treated with some caution. The issue of generalisability to other settings or countries was not addressed.

Supported in part by a grant from the Cochlear Corporation, Englewood, Colorado, USA.