Does Probe-Tube Verification of Real-Ear Hearing Aid Amplification Characteristics Improve Outcomes in Adults? A Systematic Review and Meta-Analysis

Abstract

This systematic review, the first on this topic, aimed to investigate if probe-tube verification of real-ear hearing aid amplification characteristics improves outcomes in adults. The review was preregistered in the Prospective Register of Systematic Reviews and performed in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. After assessing more than 1,420 records from seven databases, six experimental studies (published between 2012 and 2019) met the inclusion criteria; five were included in the meta-analyses. The primary outcome of interest (hearing-specific, health-related quality of life) was not reported in any study. There were moderate and statistically significant positive effects of probe-tube real-ear measurement (REM), compared with the manufacturer's initial fit, on speech intelligibility in quiet settings (standardized mean difference [SMD]: 0.59) and user's final preference (proportion difference: 52.2%). There were small but statistically significant positive effects of REM on self-reported listening abilities (SMD: 0.22) and speech intelligibility in noise (SMD: 0.15). The quality of evidence for these outcomes ranged from high to very low. The findings show that REMs improve outcomes statistically, but this is based on a small number of studies and a limited number of participants. It is currently unclear if the benefits are of material importance because minimum clinically important differences have not been established for most of the outcomes. Ultimately, there needs to be a cost-effectiveness analysis to show that statistically significant benefits, which exceed the minimum clinically important difference, are worth the cost involved.

Keywords: benefit; hearing aids; probe-tube microphone; real-ear measurement; systematic review.

Figure 1.

Flow Diagram of the Selection Process Based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). N = number of studies; REM = real-ear measurement; HA = hearing aids; RMS = root mean square.

Figure 2.

Forest Plot Comparing Self-Reported Listening Ability With REM Fitting Versus Initial Fit Using Fixed-Effects Meta-Analysis. The size of the square denotes the weight of each study, and the whiskers represent the 95% confidence interval around the effect size. Diamonds represent the pooled effect size and its 95% confidence interval. SMD = standardized mean difference; SE = standard error; IV = inverse of variance; CI = confidence interval; REM = real-ear measurements.

Figure 3.

Forest Plot Comparing Speech Intelligibility in Quiet Settings With REM Fitting Versus Initial Fit Using Random-Effects Meta-Analysis. The size of the square denotes the weight of each study, and the whiskers represent the 95% confidence interval around the effect size. Diamonds represent the pooled effect size and its 95% confidence interval. SMD = standardized mean difference; SE = standard error; IV = inverse of variance; CI = confidence interval; REM = real-ear measurements.

Figure 4.

Forest Plot Comparing Speech Intelligibility in noise With REM Fitting Versus Initial Fit Using Fixed-Effects Meta-Analysis. The size of the square denotes the weight of each study, and the whiskers represent the 95% confidence interval around the effect size. Diamonds represent the pooled effect size and its 95% confidence interval. SMD = standardized mean difference; SE = standard error; IV = inverse of variance; CI = confidence interval; REM = real-ear measurements.

Figure 5.

Forest Plot Comparing Sound Quality With REM Fitting Versus Initial Fit Using Random-Effects Meta-Analysis. The size of the square denotes the weight of each study, and the whiskers represent the 95% confidence interval around the effect size. Diamonds represent the pooled effect size and its 95% confidence interval. SMD = standardized mean difference; SE = standard error; IV = inverse of variance; CI = confidence interval; REM = real-ear measurements.

Figure 6.

Forest Plot of Comparison: Users’ Final Preference for REM Fitting or Initial Fit Using Fixed-Effects Meta-Analysis. The size of the square denotes the weight of each study, and the whiskers represent the 95% confidence interval around the effect size. Diamonds represent the pooled effect size and its 95% confidence interval. SE = standard error; IV = inverse of variance; CI = confidence interval; REM = real-ear measurements.