[Speech audiometric outcome parameters in clinical trials on hearing improvement]

When comparing clinical studies nationally and internationally, there is great heterogeneity in the applied audiometric outcome parameters. Beside different frequencies included in pure-tone audiometry and the resulting averages, the word recognition scores are measured at varying sound pressure levels, i.e., either with a fixed sound pressure level or with a fixed sensation level. However, a comparison of studies, e. g., in meta-analysis, requires comparable outcome parameters.

In this study, the influence of speech-audiometric outcome parameters on the outcome reporting of hearing therapies is studied.

Before and after a conservative or a surgical treatment aimed at hearing improvement, 25 patients with hearing impairment were tested with the German Freiburg speech intelligibility test with monosyllables and numbers at various levels, and with the German Oldenburg sentence test in quiet. Additionally, 49 subjects with normal hearing were tested.

In a comparison of measurement methods (outcome parameters), the hearing improvement measured using constant sound pressure levels for speech audiometry was significantly greater and therefore more sensitive than using constant sensation levels.

To test changes in hearing in clinical studies, fixed sound pressure levels should be preferred to fixed sensation levels. For the development of standardized outcome parameters for measuring speech intelligibility in quiet, fixed sound pressure levels or measurement of speech reception thresholds should be selected.