Test-Retest Reliability of the Daily Phonotrauma Index in Vocally Healthy Females

Objective: Phonotraumatic Vocal Hyperfunction (PVH) is a voice disorder characterized by chronic trauma to the vocal folds resulting in nodules or polyps. While objective and perceptual voice data for patients with PVH can be obtained in a clinical environment, its relation to patients’ habitual vocal behavior is unclear. Thus, ambulatory monitoring has been used to quantify and qualify real-world voice use. Previous studies have shown that the Daily Phonotrauma Index (DPI) from ambulatory monitoring can classify PVH patients from controls and is correlated to expected changes post-surgery, post-therapy, the combination of surgery and therapy, and large changes in self-reported vocal status. However, the DPI’s test-retest reliability has never been investigated. This study compares the DPI across two monitoring periods six months apart in vocally healthy participants to better understand normal variability of the DPI. We hypothesized that the DPI and its underlying measures of neck-skin acceleration magnitude (NSAM) skewness and the standard deviation (SD) of the difference between the first two harmonics (H1-H2) will classify this group as normal (DPI 12 hours per day. Two rounds of monitoring occurred approximately six months apart. Dependent sample T-tests were used to compare the mean and variance of metrics.

Results: The DPI, NSAM skew, and H1-H2 SD were not significantly different between the first week and monitoring six-months later; -0.61±.65 and -0.64±.66, -.13±.23 and -.09±.26, 6.92±.86 and 6.84±.88, respectively; differences that did not meet the level of statistical significance.

Conclusions: As hypothesized, the DPI and its features (NSAM skewness, H1H2 SD) remained in the normative values and did not change between multiple week-long recordings, supporting a strong test-retest reliability for the DPI. It is thought that higher-level distributional characteristics (skew, SD) represent long-term behavioral tendencies and should not change over time. Future work can further evaluate DPI’s test-retest reliability for patients who elect not to have therapy and those who complete therapy.