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Table 4 Summary of all primary and secondary outcome instruments used across all 228 clinical trials. Instruments have been grouped according to the major domain categories reported in Table 3, as well as those instruments that were not clearly specified by the authors. Note that the total refers to the number of instruments across all 228 trials. The remainder are reported in Additional file 6. Percentages are rounded so, for example, 0 % denotes a value that is <0.5 %

From: Systematic review of outcome domains and instruments used in clinical trials of tinnitus treatments in adults

  Primary outcome instruments Secondary outcome instruments
  Number Percentage (%) Number Percentage (%)
(1a) Investigator-administered tests relating to the tinnitus percept:
 Tinnitus loudness matching 20 4 % 16 3 %
 Tinnitus pitch matching 9 2 % 22 4 %
 Minimum masking level 5 1 % 12 2 %
 Loudness discomfort level 3 1 % 2 0 %
 Tinnitus bandwidth matching 0 - 2 0 %
(1b) Patient-reported numerical rating scales relating to the tinnitus percept:
 Tinnitus loudness 37 8 % 24 4 %
 Tinnitus pitch 0 - 2 0 %
(2a) Patient-reported questionnaire instruments relating to the impact of tinnitus:
 Tinnitus Handicap Inventory 77 15 % 31 5 %
 Tinnitus Questionnaire (German version) 29 6 % 11 2 %
 Tinnitus Questionnaire (English version) 5 1 % 0 -
 Tinnitus Functional Index 18 4 % 3 1 %
 Tinnitus Beeinträchtigungs Fragebogen 13 3 % 8 1 %
 Tinnitus Severity Index 12 2 % 1 0 %
 Tinnitus Reaction Questionnaire 11 2 % 2 0 %
 Tinnitus Handicap Questionnaire 8 2 % 5 1 %
 Mini-Tinnitus Questionnaire 6 1 % 0 -
 Tinnitus Effects Questionnaire 2 0 % 0 -
 Tinnitus diary 2 0 % 0 -
 Tinnitus Psychological Impact Questionnaire 2 0 % 0 -
 Tinnitus Severity Scale 0 - 6 1 %
 Tinnitus Acceptance Questionnaire 0 - 6 1 %
(2b) Patient-reported numerical rating scales relating to the impact of tinnitus:
 Tinnitus distress 7 2 % 8 1 %
 Tinnitus annoyance 21 4 % 14 2 %
 Tinnitus awareness 10 2 % 2 0 %
(3) Patient-reported questionnaire instruments relating to other co-occurring complaints:
 Beck Depression Inventory 7 1 % 13 2 %
 Hospital Anxiety and Depression Scale 7 1 % 27 5 %
 Perceived Stress Questionnaire 3 1 % 0 -
 Spielberger State and Trait Anxiety Inventory 3 1 % 3 1 %
 Brief-Coping with Problems Experienced 2 0 % 0 -
 Pittsburgh Sleep Quality Index 2 0 % 2 0 %
 Hearing Handicap Inventory 1 0 % 4 1 %
 Hyperacusis questionnaire (undefined) 1 0 % 2 0 %
 Attention and Performance Self-assessment Scale 0 - 2 0 %
 Befindlichkeitsskala 0 - 2 0 %
 Cognitive Failures Questionnaire 0 - 2 0 %
 Depression Anxiety and Stress Scale 0 - 3 1 %
 Insomnia Severity Index 0 - 7 1 %
 Major Depression Inventory 0 - 5 1 %
 Sleep Questionnaire (undefined) 0 - 3 1 %
(4a) Patient-reported questionnaire instruments relating to health-related quality of life:
 Clinical Global Impression Scale 4 1 % 14 2 %
 36-item short form Health Survey 2 0 % 6 1 %
 WHOQOL-BREF 0 - 10 2 %
 EuroQoL 0 - 2 0 %
 Quality of Life Inventory 0 - 2 0 %
(4b) Patient-reported numerical rating scales relating to health-related quality of life:
 Quality of Life (tinnitus) 5 1 % 6 1 %
 Quality of Life 4 1 % 1 0 %
(5) Technical and laboratory measurements relating to body structures and functions:
 Pure tone audiometry 15 3 % 23 4 %
 Speech audiometry (various types) 6 1 % 11 2 %
 Electroencephalography 4 1 % 5 1 %
 Blood chemistry 2 0 % 10 2 %
 Positron Emission Tomography 2 0 % 0 -
 Electrocardiogram 1 0 % 4 1 %
 Digit symbol test 1 0 % 2 0 %
 Blood drug levels 0 - 4 1 %
 Magnetic Resonance Imaging 0 - 3 1 %
 Otological examination 0 - 4 1 %
 Otoscopy 0 - 2 0 %
 Psychoacoustic assessment (undefined) 0 - 3 1 %
 Tympanometry 0 - 2 0 %
 Urine analysis 0 - 2 0 %
(6) Measures of adverse events or harms:
 Adverse events/Side effects 4 1 % 30 5 %
(7) Measures of satisfaction: No instruments reported
(8) Measurement instruments of treatment-related outcomes:
 Withdrawal rate 2 0 % 2 0 %
(9) Measurement of interest unclear or not specified by the authors:
 Cannot code 20 4 % 52 9 %
 Other numerical rating scale (undefined) 18 4 % 29 5 %
 Questionnaire (authors’ own) 15 3 % 13 2 %
 Numerical rating scale of tinnitus severity 12 2 % 1 0 %
 Not specified 8 2 % 18 3 %
Total 505 87 % 579 85 %