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 %

 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 %

 Tinnitus loudness

37

8 %

24

4 %

 Tinnitus pitch

0

-

2

0 %

 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 %

 Tinnitus distress

7

2 %

8

1 %

 Tinnitus annoyance

21

4 %

14

2 %

 Tinnitus awareness

10

2 %

2

0 %

 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 %

 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 %

 Quality of Life (tinnitus)

5

1 %

6

1 %

 Quality of Life

4

1 %

1

0 %

 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 %

 Adverse events/Side effects

4

1 %

30

5 %

(7) Measures of satisfaction:

 Withdrawal rate

2

0 %

2

0 %

 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 %