Supplementary Material for: Validation of Speech Handicap Index-Tamil (SHI-T) among persons treated for Head and Neck Cancer

Introduction: The Speech Handicap Index (SHI) is a self-reported measure that facilitates assessing the speech difficulties of patients with head and neck cancer (HNC). A valid outcome measure in Tamil language is vital to evaluating the speech difficulties among Tamil-speaking persons treated for HNC.
Objectives: This study aimed to adapt and assess the reliability and validity of using the SHI-Tamil among Tamil-speaking individuals treated for HNC.
Materials and methods: The Tamil version of SHI was finalized by reviewing an existing version through back translation, expert reviews, and cognitive interviews with participants in a pilot study. Ninety-five patients with HNC and 61 healthy adults completed the SHI-T and speech domain of the University of Washington Quality of Life questionnaire V4. As many as 21 patients completed the SHI questionnaire again within 2 weeks to assess test-rest reliability.
Results: The Tamil-adapted version of the SHI demonstrated excellent internal consistency (α=0.97) and very strong test-retest reliability (ρ=0.87). SHI scores significantly differed between the patients (Mdn=16.0, IQR=65) and the healthy group (Mdn=0, IQR=1). Within the patient group, SHI scores distinguished patients with and without self-reported speech concerns and the type of cancer treatment in the tongue cancer subset. The total and domain scores of SHI correlated significantly with the University of Washington Quality of Life questionnaire V4 (r > 0.8), indicating the construct validity of SHI.
Conclusion: The Tamil version of SHI is a culturally relevant, valid, and reliable patient-reported outcome measure for assessing speech difficulties among persons treated for HNC.