Maximum phonation time: Surrogate marker in ALS (Tabor Gray et al., 2023)

Purpose: The increased use of telehealth practices has created a critical need for home-based surrogate markers for prognostic respiratory indicators of disease progression in persons with amyotrophic lateral sclerosis (pALS). Given that phonation relies on the respiratory subsystem of speech production, we aimed to examine the relationships between maximum phonation time (MPT), forced vital capacity, and peak cough flow and to determine the discriminant ability of MPT to detect forced vital capacity and peak cough flow impairments in pALS.

Method: MPT, peak cough flow, forced vital capacity, and ALS Functional Rating Scale scores were obtained from 62 pALS (El-Escorial Revised) every 3 months as part of a longitudinal natural history study. Pearson’s correlations, linear regressions, and receiver operator characteristic curve analyses with the area under the curve (AUC), sensitivity, specificity, and likelihood ratios were calculated.

Results: The mean age of pALS was 63.14 ± 10.95 years, 49% were female, and 43% had bulbar onset. MPT predicted forced vital capacity, F(1, 225) = 117.96, p < .0001, and peak cough flow, F(1, 217) = 98.79, p < .0001. A significant interaction was noted between MPT and ALS Functional Rating Scale–Revised respiratory subscore for forced vital capacity, F(1, 222) = 6.7, p = .010, and peak cough flow, F(1, 215) = 4.37, p = .034. The discriminant ability of MPT was excellent for peak cough flow (AUC = 0.88) and acceptable for forced vital capacity (AUC = 0.78).

Conclusions: MPT is a simple clinical test that can be measured via telehealth and represents a potential surrogate marker for important respiratory and airway clearance indices. Further larger studies are required to validate these findings with remote data collection.

Supplemental Material S1. Classification accuracies for maximum phonation time (MPT) to identify forced vital capacity (FVC) less than 50% and peak cough flow (PCF) less than 160 L/min.

Tabor Gray, L., Donohue, C., Vasilopoulos, T., Wymer, J. P., & Plowman, E. K. (2023). Maximum phonation time as a surrogate marker for airway clearance physiologic capacity and pulmonary function in individuals with amyotrophic lateral sclerosis. Journal of Speech, Language, and Hearing Research, 66(4), 1165–1172. https://doi.org/10.1044/2022_JSLHR-22-00522