Proposal for a Core Outcome Set of Measurement Instruments to Assess Quality of Voice in Adductor Spasmodic Dysphonia Based on a Literature Review

Uniform evaluation of treatment effect on the quality of voice in adductor spasmodic dysphonia (AdSD) is challenging due to the broad variety of available outcome measurement instruments (OMIs). The European Laryngological Society categorized five types of measurement domains for voice quality evaluations: patient-reported outcome measures, perceptual analyses, acoustic analyses, visual analyses, and aerodynamic measurements. The aim of this study was to propose a core outcome set (COS) for these domains, enabling systematic assessments of treatment effects on the quality of voice in patients with AdSD. The PubMed, Embase, and Cochrane databases were searched for eligible studies published before July 2019. The results were systematically analyzed following the protocol of the COnsensus-based Standards for the selection of health Measurement INstruments/Core Outcome Measures in Effectiveness Trials initiative. The proposed COS is based on the prevalence of OMIs, quality of the included studies, criteria for good measurement properties, and correlations to other OMI domains. A total of 76 articles were included, with nearly all studies and OMIs found to be of moderate or low quality. The 19 studies that reported on the correlation of OMIs demonstrated conflicting results. Appraising the best available evidence, our proposed COS consisted of patient-reported outcome measures (voice handicap index), perceptual measurements (grade, roughness, breathiness, strain, and voice breaks) and acoustic measurements (voice breaks, voice onset time, aperiodicity, and multiparameter algorithms). A review of OMIs evaluating treatment effects in AdSD was conducted. Based on this review, a uniform COS was proposed. However, evidence for the selected instruments was limited. Further exploration into the validity and reliability of OMIs for AdSD is recommended.