Methodological Considerations for the Acoustic Voice Quality Index in Persian-Speaking Populations: A Technical Note

OBJECTIVE: This study aims to technically compare, evaluate, and discuss the methodological design, psychometric properties, and external validity of existing studies validating the Acoustic Voice Quality Index (AVQI) for Persian-speaking populations. Given discrepancies in reported cut-off values and AVQI implementation protocols, this technical note seeks to provide evidence-based recommendations for clinicians and researchers applying the AVQI to explore voice quality in Persian speakers. METHOD: A comprehensive literature search was systematically conducted across multiple electronic databases to identify peer-reviewed studies validating AVQI in Persian-speaking populations. Inclusion criteria required studies to assess AVQI using both disordered and healthy voice samples, report relevant statistical and methodological details, and be published in English or Persian. Three studies were found, including Aghajanzadeh et al, Rafiei et al, and Zainaee et al based on the inclusion criteria. Methodological quality was also evaluated using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) checklist, and an expert panel analyzed consistencies and inconsistencies among these studies. RESULTS: All three studies demonstrated acceptable concurrent validity and diagnostic accuracy for the AVQI in Persian-speaking populations. However, notable inconsistencies were observed in methodological design and AVQI optimal cut-off thresholds. Zainaee et al evaluated both AVQI version 2.03 and version 3.01, whereas Aghajanzadeh et al and Rafiei et al only used version 3.01. Differences in speech stimuli, vowel duration, rater experience, and regional dialectal diversities contributed to variability in psychometric properties such as sensitivity and specificity. QUADAS-2 assessments showed low risk of bias and high external validity across studies. CONCLUSION: Despite strong psychometric properties for the AVQI in Persian-speaking populations, inconsistencies across studies' methodologies and findings might challenge its clinical and research applicability. Clinicians are encouraged to align their assessment protocols with those of the studies from which they adopt optimal thresholds. Future research should address regional intra-linguistic variations, optimize speech task standardization, and precisely clarify participant demographics to improve AVQI implementation in Persian-speaking populations and other languages with various dialects.