Toward development of a tinnitus magnitude index

OBJECTIVES: The aim of the study was to provide preliminary evidence of a unique "tinnitus magnitude" domain describing intensity of tinnitus perception that will assist in the development of a cognitive-behavioral mediation model of psychological distress associated with tinnitus. DESIGN: A sample of 347 participants with tinnitus was previously recruited from four audiology clinics for the purpose of developing a tinnitus distress measure, the Tinnitus Functional Index (TFI). From the questions used for TFI development, potential tinnitus magnitude items were selected by including those that minimally overlapped with tinnitus reactions. The three items having the least overlap were analyzed retrospectively to assess internal consistency, test-retest reliability, group differences using demographics and tinnitus-relevant descriptive variables, and discriminant validity. The three-item scale was developed in an effort to establish a model for prospective development of a Tinnitus Magnitude Index (TMI) that would assess the magnitude of tinnitus variables independent of reactions to tinnitus. RESULTS: Internal consistency (α = 0.86) and repeated measures tests (r = 0.74, df = 29, p < 0.001) indicate the three-item scale is reliable. Discriminant validity was supported by only moderate correlations (r ≥ 0.30 and r ≤ 0.69) of the scale with the Tinnitus Handicap Inventory (r = 0.62), the Beck Depression Inventory for Primary Care (r = 0.38), and the seven independent domains of tinnitus reactions measured using subscales of the TFI (r = 0.49 to 0.72). Correlations between the scale and two tinnitus reactions (distress) subscales were high (r > 0.70) as compared with moderate correlations. CONCLUSIONS: This study involved a retrospective analysis of data from questions that were originally evaluated for use in a tinnitus outcome questionnaire. The analysis was conducted to establish a model for prospective development of a TMI. Results of this analysis suggest that a TMI can be developed that would provide a reliable and valid measure of tinnitus magnitude that overlaps minimally in content with measures of cognitive, behavioral, and emotional tinnitus reactions. A fully validated TMI would provide a measure of tinnitus magnitude that is not confounded by emotional reactions to tinnitus or general depressive symptoms and would be useful in developing a testable model of psychological distress due to tinnitus. Although the primary goal is to develop a measure of tinnitus magnitude that predicts cognitive, behavioral, and emotional reactions to tinnitus, a TMI may also have utility in assessing this construct in clinical settings.