Integrating Distribution-Based and Anchor-Based Techniques to Identify Minimal Important Change for the Tinnitus Functional Index (TFI) Questionnaire

Abstract

The Tinnitus Functional Index (TFI) was developed to be responsive to small treatmentrelated changes in the impact of tinnitus. Yet, no studies have integrated anchor-based and distribution-based techniques to produce a single Minimal Important Change (MIC) score. Here, we evaluated the responsiveness and interpretability of the TFI, determining for the first time a robust MIC score in a UK clinical population. Two-hundred and fifty-five patients with tinnitus participated in this prospective longitudinal validation study. Distribution-based estimates (Standard Error of Measurement, Smallest Detectable Change and Effect size) and anchor-based estimates of important change (minimal clinically important difference and Receiver Operator Curve optimal value) were calculated and then integrated using a visual anchor-based MIC distribution plot. A reduction in score of –14 was determined as the MIC estimate that exceeds the measurement error, most of the variability and reliably identifies patients demonstrating true improvement. It is therefore recommended that a reduction of 14 points should be used as a minimum change required when calculating statistical power and sample size in tinnitus intervention studies and assessing patients in clinical practice.