Frameworks, Terminology and Definitions Used for the Classification of Voice Disorders: A Scoping Review

A challenge for clinicians and researchers in laryngology is a lack of international consensus for an agreed framework to classify homogenous groups of voice disorders. Consistency in terminology and agreement in how conditions are classified will provide greater clarity for clinicians and researchers. This scoping review aimed to examine the published literature on frameworks, terminology, and criteria for the classification of voice disorders. Seven online databases (MEDLINE, Embase, CINAHL, PsycInfo, Scopus, Cochrane Collaboration, Web of Science) and grey literature sources were searched. Studies published from 1940 to 2021 were included if they provided a descriptive detail of a classification framework structure and described the methodological approaches to determine classification. A narrative synthesis of the main concepts including terminology, classification criteria, grouping of conditions, critical appraisal items and gaps in research was undertaken. A total of 2,675 publications were screened. Twenty sources met inclusion criteria, including published articles and grey literature. Thirty-five classification groups and over 150 sub-groups were described. The classification group labels, and criteria for inclusion of conditions varied across the frameworks. Several key themes in terminology and criteria useful for classification are discussed, and a core set of suggested terms and definitions are presented. The quality of research on classification frameworks for voice disorders is low and not one system encompasses all voice disorders across the whole spectrum. Continued high quality research using consensus methodology and inter-rater reliability scores is recommended to develop and test an internationally agreed classification framework for voice disorders.