Validation of the Acoustic Voice Quality Index, Version 03.01, in French

The Acoustic Voice Quality Index (AVQI), version 03.01, is a tool for quantitative assessment of the overall severity of dysphonia. It is based on the recordings of a sustained vowel and part of a text read aloud. For the Dutch sample, 34 syllables must be read aloud to balance the duration of the two tasks. The first part of this study thus aimed to determine how many syllables of a commonly used text in the French-speaking part of Belgium should be used to achieve the same balance. The psychometric qualities of the AVQI have been confirmed by numerous publications in various languages. However, its validation in French relies on a small cohort of patients, who were not native French speakers. Furthermore, version 03.01 of the AVQI has not yet been validated at all on French samples. Hence, the main aim of this study was to assess the criterion-related concurrent validity and diagnostic accuracy of the AVQI 03.01 applied to a sample of native French speakers.

For the first part of this study, the optimal part of the text to be used for the AVQI was identified, taking into account both its phonemic contents and its time balance with the sustained vowel. For the validation study, 90 recordings from the University Hospital of Liège's ENT caseload database were used, as well as 30 new recordings of normophonic individuals, composing a control group. Four judges assessed the recordings using the G parameter of the GRBAS scale. Once the intra- and inter-rater reliability of the perceptual ratings was confirmed, the AVQI 03.01's criterion validity was assessed on the French sample. The diagnostic accuracy of the AVQI 03.01 in French was measured, and the cut-off score allowing for the greatest diagnostic precision determined.

The most appropriate syllable number of the text to be read aloud was found to be 27, in order to balance the time analyzed for both the sustained vowel and the continuous speech. Regarding the validation study, intra-rater reliability was substantial for each of the four vocologists (κ_mean = .778, P < 0.0001), and inter-rater reliability was high (W = .895, P < 0.0001). The Spearman correlation between the perceptual judgments and the AVQI 03.01 score was strong (r_s = .84, P < 0.0001). The receiver operating characteristic-curve parameters indicated that the ideal cut-off score allowing for the highest diagnostic accuracy of the AVQI, version 03.01, applied to a French sample is 2.33, with a sensitivity of 59.8%, a specificity of 100%, an infinite positive likelihood ratio (LR+) and a negative likelihood ratio (LR-) of 0.4.

This study confirms the external validity of the AVQI 03.01 when applied on a French 27-syllable sample. The AVQI 03.01 is a robust, ecologically valid objective measure of overall voice quality. The cut-off score to be used is 2.33. However, clinicians should be cautious when the AVQI score is lower than 2.33. The AVQI 03.01 does not yield a sufficiently low negative likelihood ratio to be sure that this score indeed indicates normophonia. Also, taking into account the limitations regarding the perceptual judgements used in this study, a replication study should be carried out in order to confirm the cut-off score.