Table 3 Description and test metrics of outcome measures

 Dizziness Handicap Inventory (DHI)

25 items, each item has 3 alternative scores 0 (no), 2 (sometimes) and 4 (yes) giving a score range of 0–100 DHI points [37]. Higher scores indicate greater perceived disability; 0–30; mild, 31–60; moderate, 61–100; severe [38]

Cut-off 29 points,

MIC 11 DHI points,

ICC 1,1 0.90 [39].

 Preferred gait velocity (m/s)

Participants walked at normal pace, down an 8-m pathway, timed in the middle 6 m. It was timed using a stopwatch from when the first foot passed the start point to when the last foot passed the stop point.

Mean velocity over two trials were calculated

Substantial meaningful change 0.1 m/s [40],

ICC (3.1): 0.88 (CI 0.81–0.98) [41]

 The shortened version of the Vertigo Symptom Scale (VSS)

15 items, each scoring from 0 (never)

to 4 (very often) giving a score range of 0–60. Higher scores indicate greater symptom severity [42]. Severe dizziness ≥ 12 [42]

Norwegian version cut-off, 6.5 points [43].

Clinically significant change in original version ≥ 3 points [44].

ICC Norwegian version, 0.89 [43]

 Agoraphobic Cognitions Questionnaire (ACQ)

14 items, each rated on a scale ranging from 1 (thought never occurs when I am nervous) to 5 (thought always occurs when I am nervous) [45]. Measures fear of fear.

The mean score is reported, and higher scores imply greater levels of fear

Cronbach’s alpha for outpatients with agoraphobia, 0.80 [45]

 Body Sensation Questionnaire (BSC)

18 items, each with a score range from

1 (not at all frightened by the sensations) to 5 (extremely frightened by this sensation). The mean score reported, and higher scores implies greater fear of somatic sensations [45]

Cronbach’s alpha for outpatients with agoraphobia, 0.87 [45]

 Mobility Inventory of Agoraphobia-Alone (MIA)

27 items, each rated from 1 (never avoids) to 5 (always avoids). The mean score is reported and, and higher scores indicate greater avoidance behaviour

Cronbach’s alpha in agoraphobia, 0.96 [46]

• Attack frequency

Measures frequency of distress related to sudden onsets of episodes with 4 or more strong sensations of dizziness and dizziness related symptoms on a 5-point scale ranging from 0 (no attacks) to 4 (one or more attacks per day). Adapted from the Panic Attack Scale [47]

• Attack severity

Severity rating of the degree of distress related to the episodes described above. Numeric rating scale with a score range 0–8. Higher scores indicates increased symptom-related distress/disability. Adapted from the Panic Attack Scale [47]

Hospital Anxiety and Depression Scale (HADS)

14 items, each rated from 0 (not present) to 3 (considerable), giving a score range of 0–42 points [48]. Higher scores indicates greater psychological distress

Cut-off 12 points,

Cronbach’s alpha, 0.88. [49]

EQ-5D-5 L

Generic instrument describing and valuing health [50].

• EQ-5D-5 L

Five dimensions, each rated from 1 to 5. Higher scores indicate increased health problems [51]

• EQ-5D-5 L Vas

Score range 0–100%. Higher scores indicate better perceived health-related quality of life

MCID in stroke,:8.61–10.82 [52]

Subjective Health Complaints (SHC)

29 items, each item is scored from 0 (no complaints) to 3 (serious complaints). Higher scores indicate greater severity of complaint. Split into 5 subcategories: Musculoskeletal 8 items (score 0–24), Pseudoneurology 7 items (score 0–21), Gastrointestinal 7 items (score 0–21), Flu 2 items (score 0–6) and Allergy 5 items (score 0–15) [53]

Cronbach’s alpha musculoskeletal pain, 0.74;

Pseudoneurology, 0.73;

Gastrointestinal, 0.62;

Allergy, 0.58; and

Flu, 0.67 [53]

Chalder’s Fatigue Questionnaire (CFQ)

13 items. The first 11 items are scored from 0 (better than usual) to 3 (much worse than usual), giving a score range of 0–33. The last 2 items rate duration and constancy of fatigue [54]. Higher scores indicating more fatigued

Cronbach’s alpha in Norwegian population, 0.86 [55]

Patient Specific Functional Scale (PSFS)

Registers up to 3 activities that participants find difficult. In addition, the level of difficulty is rated on an 11-point scale [56], where 0 maximum difficulty and 10 is no difficulty

Reliability established in various musculoskeletal problems (ICC 0.76–0.97) [57]

MCID in various musculoskeletal problems, 0.99–2.5 [57]

Patient Global Impression of Change (PCIG)

1item, rated from 1 (very much improved) to 7 (very much worse), with a score of 4 indicating no change [58]

 Dual-task walking

Similar walking protocol as for preferred gait velocity, with an added task of counting backwards by 3 out loud, while walking. Each trial was timed and the numbers of miscounts were documented. Mean velocity, and mistakes over 2 trials calculated

 Fast gait velocity (m/s)

Similar protocol to preferred gait velocity; however, participants were asked to walk as fast as possible

 Clinical dynamic visual acuity (CDVA)

Evaluates gaze stability by assessing visual acuity using examiner-mediated head oscillations at 2 Hz relative to head being stationary

Cut-off ≥ 3 lines indicates potential vestibular hypofunction [59]. Reliability in bilateral peripheral hypofunction ICC (2.2): 0.94 [60]

 Head-movement-induced dizziness

Perceived dizziness reported using the Numeric Rating Scale (NRS) on 2 conditions: 1 while sitting stationary, and 1 after 1 min of active head oscillations at 1 Hz (following a metronome). Score range 0 (no dizziness) to 10 (as bad as it can be), with higher scores indicating higher perceived intensity of head-movement-induced dizziness. Difference between the two conditions will also be calculated

VAS head-movement-induced dizziness [41],

reliability 0.48 for all subjects,

reliability 0.82 for male subjects

 Grip strength

Maximal grip strength in both hands assessed using a hand-held dynamometer. Measured in kg. Averaged between 2 trials calculated for each hand

Genuine change in healthy adults, 6 kg [61]

 Body sway while standing

Assessed using the modified test for interaction and balance (mCTSIB) with arms crossed over the chest, using the HURlabs balance trainer BTG4; 4 conditions tested: standing with eyes open and closed, on a firm surface or on a foam cushion. Each trial is timed for 30 s

ICC in healthy subjects, 0.91–0.97 [62]

 Elements from the Global Physiotherapy Examination (GPE)

4 elements from the main domain Movement of the GPE examination were selected [17, 36]. The items include lumbo-sacral flexion, head-nod flexion, shoulder retraction and elbow drop.

Score range − 2.3 to 2.3, scored in relation to a predefined standard (0) [36]

ICC 2.1 lumbo-sacral flexion, 0.82;

ICC 2.1 head-nod flexion, 0.84;

ICC 2.1 shoulder retraction, 0.75;

ICC 2.1 elbow drop, 0.89 (personal communication: A. Kvåle)