Determining the Sample Size for Future Trials of Hearing Instruments for Unilaterally Deaf Adults: An Application of Network Meta-analysis.

Objective: Previous trials have compared the efficacy of hearing instruments to no intervention in adults with single-sided deafness (SSD) or the relative efficacy of different instruments. Network meta-analysis (NMA) was used to refine estimates of effect sizes to determine required sample sizes for further trials.

Data Sources: PubMed, EMBASE, MEDLINE, Cochrane, CINAHL, and DARE databases were searched with no restrictions on language, with studies to February 2015 included.

Study Selection: Studies were included that 1) assessed hearing instruments in adults with SSD; 2) compared instruments with other instruments, placebo, or no intervention; 3) measured speech perception in quiet/noise and listening ability; 4) were prospective controlled or observational studies.

Data Extraction: The following data were extracted: sample size in each group, type of intervention and comparator, type of outcomes, mean outcome scores and their 95% confidence intervals.

Data Synthesis: Random-effects meta-analysis was conducted to determine pooled effects for each outcome based on direct evidence alone. NMA used graph-theoretical method to determine pooled effects based on indirect evidence. Sample size calculations were conducted for each outcome for each class of evidence.

Conclusions: The incorporation of indirect evidence had substantial impacts on some effect sizes but negligible impacts on other effects. The most notable impacts were on self-reported listening ability and measures of speech perception in noise. Changes in effect size estimates and required sample sizes resulting from the incorporation of indirect evidence highlight areas of uncertainty where trials may be feasible to conduct.