The authors concluded that a methodologically weak but consistently positive body of effectiveness evidence supported the use of unilateral cochlear implants in adults with severe to profound deafness. The conclusions reflected the limited evidence; this limitation should be borne in mind when interpreting the findings.

To compare the clinical and cost-effectiveness of multi-channel unilateral cochlear implants with non-technological support or acoustic hearing aids in adults with severe to profound deafness.

Fourteen databases were searched from inception to June 2009, including MEDLINE, EMBASE, NHS EED, DARE, the Cochrane Library, Current Controlled Trials, and National Research Register. Searches were restricted to articles in English. The search strategy was not reported in this paper but can be found in an associated Health Technology Assessment report (see Other Publications of Related Interest). Keywords were listed in the report and a full strategy was available on request from the authors. Bibliographies and reference lists were also examined for further studies.

This review was part of a larger Health Technology Assessment report of adults and children with severe to profound deafness (Other Publications of Related Interest). Randomised and non-randomised controlled trials and pre/post and cross-sectional studies of adults with severe to profound sensorineural deafness, where participants acted as their own controls, were eligible for inclusion. For inclusion, studies had to compare multichannel cochlear implants (with whole speech processing) versus either acoustic hearing aids or no technological support.

In included studies, participants had a mean age that ranged from 47.5 to 62 years old. Mean duration of deafness varied from 5.3 to 30.4 years and the outcomes reported were quality of life, speech perception and sound direction. Quality of life was measured using a variety of measurement tools and adverse events were reported.

Two reviewers independently selected studies for inclusion and disagreements were resolved by discussion.

Methodological quality was assessed following the general principles published by CRD; items included inclusion criteria, power calculation, whether the study was prospective, accounting of confounders, ethical approval reported, attrition reported, missing data and accounting of missing participants.

The number of reviewers that assessed quality was not reported.

Data were extracted independently by two reviewers for the outcomes reported.

The studies were synthesised narratively as the data were considered too heterogeneous to pool statistically.

Nine studies (including ten comparisons) were included in the review (n=1,253 participants; range 21 to 238). Six studies (seven comparisons) were prospective pre/post studies (n=981), one was a cross-sectional study (n=21), one a retrospective pre/post study (n=214) and one a controlled trial (n=37). Study quality varied; none of the studies reported sample size calculation, four accounted for confounders, four reported attrition, four accounted for all participants and two accounted for missing data. Length of follow-up ranged from three to 72 months.

Unilateral implant versus non-technological support (six studies): All except one of the included studies found an improvement with cochlear implants (significant and non significant improvements). Two studies reported significant improvements in measures of speech perception. Two studies reported significant improvements in health-related quality of life.

Unilateral implant versus acoustic hearing aids (four studies): All of the included studies found an improvement with cochlear implants (significant and non significant improvements). Two studies reported significant improvements in measures of speech perception. Two studies reported significant improvements in health-related quality of life.

Adverse events were also reported.

Four economic evaluations (five comparisons) met the inclusion criteria and presented cost utility analyses, using decision models to produce cost and utility estimates. The incremental cost effectiveness ratios reported for unilateral implantation versus no intervention were £17,625, £16,774, £11,440 or £13,300 per quality adjusted life year (QALY). The incremental cost-effectiveness ratio for unilateral implantation versus hearing aids was £27,401 per QALY. All of these values would be considered good value for money according to the NICE criteria.

The methodologically weak but consistently positive body of effectiveness evidence supported the use of unilateral cochlear implants in adults.

The review question was supported by inclusion criteria for participants, interventions and study design. A range of databases were searched, but publications in languages other than English were not eligible, so language bias was possible. The methods of study selection and data extraction were performed in duplicate, reducing the risk of reviewer error and bias; however, methods were not reported for validity assessment.

Study quality was assessed using appropriate criteria. A narrative synthesis was appropriate, given the heterogeneity of the included studies. Only a small number of studies with small sample sizes were included.

The authors conclusions reflected the limited evidence; this limitation should be borne in mind when interpreting the findings.

Practice: The authors stated that, although there are reservations regarding generalisability due to the size and quality of included studies, the positive direction of change in all cases indicates that unilateral cochlear implantation is likely to be an effective treatment for profoundly deaf adults.

Research: The authors stated that further well designed studies (with larger sample sizes, long-term follow-up and standardised outcomes) are needed to determine other factors that determine effectiveness. Full data on known and potential determinants of post-implantation speech and quality of life outcomes should be recorded. The authors also stated that there is a strong case for a national research register of all UK cochlear implant recipients.

NIHR Health Technology Assessment Programme (project number 06/59/01).

Bond M, Elston J, Mealing S, Anderson R, Weiner G, Taylor RS, Liu Z, Stein K. Effectiveness of multi-channel unilateral cochlear implants for profoundly deaf children: a systematic review. Clinical Otolaryngology 2009; 34(3): 199-211.

Bond M, Mealing S, Anderson R, Elston J, Weiner G, Taylor RS, Hoyle M, Liu Z, Price A, Stein K. The effectiveness and cost-effectiveness of cochlear implants for severe to profound deafness in children and adults: a systematic review and economic model. Health Technology Assessment 2009; 13(44): 1-171.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.