The literature describes many clinical tests of balance. Some tests selectively evaluate standing or walking balance; some tests have only one component, others have many subtests. Some tests are designed for frail, institutionalized individuals, other tests are designed for relatively healthy people. No evidence suggests which tests are best for screening particular disorders, or whether or not both standing balance and walking balance should be tested. Most studies have examined falls prediction. No studies have examined the value of a battery of inexpensive screening tests to suggest which individuals might have vestibular impairments and might benefit from referral for further testing.
The goal of screening is to identify patients who may benefit from in-depth diagnostic testing. An ideal screening test requires minimal equipment, is easy to administer in a short period of time, and has high sensitivity, thus minimizing the likelihood of a false negative result. For example the well-known Berg Balance scale, which was designed to evaluate standing balance in elderly patients [1
], fits that description. It is user-friendly, includes 14 brief subtests, uses minimal, inexpensive equipment, and is easily scored by a staff member using a 5-point ordinal scale. It predicts falling in seniors [3
], differentiates among normals, people with Parkinson’s disease and people with peripheral neuropathy [4
], and is sensitive to change after vestibular rehabilitation [5
]. With in-patient stroke patients it detected fallers well but specificity to ambulatory fallers increased when the Berg was combined with a test of walking [6
]. The Berg uses a single cut-point to separate normal from abnormal scores [1
]. The finding that age and sex affect scores [7
] suggests that multiple cut-points might be more useful, however.
Computerized dynamic posturography, using the Equitest (Neurocom International, Inc), measures changes in the center of pressure as the body sways over the feet during various conditions of quiet standing on a force platform. It has been considered the criterion standard since publication of the seminal paper by Nashner and his colleagues [8
]. In the six conditions of the Sensory Organization Test (SOT) subjects are tested on six combinations of visual (eyes open reliable, vs. eyes closed, eyes open unreliable) and proprioceptive (reliable vs. unreliable) conditions. The most challenging conditions are sensitive to people with histories of falls [9
] and show changes after space flight [10
]. All subtests show changes with age [11
]. The equipment, however, is large and not easily moved, and the cost may be beyond the budget of many small clinics, limiting its use in many clinical environments.
The Get Up and Go Test [12
], sharpened by timing it as the Timed Up and Go (TUG) [13
] is a test of walking balance, designed to identify elderly fallers. It is easy for even cognitively impaired elderly people to understand, requires minimal equipment and is easy to score and interpret [14
]. It differentiates elderly patients at moderate to high risk of falling from individuals at low risk for falling [15
], elderly, institutionalized patients from community-dwelling seniors [16
], and community-dwelling seniors who fall from non-fallers [17
]. On an in-patient stroke unit, compared to the Berg the TUG had slightly greater specificity to fallers but less sensitivity to ambulatory non-fallers [6
The Dynamic Gait Index (DGI) [18
] also tests walking balance. Similar to the Berg, it uses minimal equipment, has several subtests, and is easily scored. It has moderate sensitivity to patients with balance disorders [19
] but good sensitivity to fallers with vestibular disorders [20
]. It is well-constructed and particularly useful for community-dwelling older adults with balance problems [22
]. Scores on the DGI and the Berg are moderately correlated [23
]. Inter-rater reliability on individual test items varies from poor to excellent [24
]. Similarly, test-retest reliability ranges from poor to excellent, depending on the subtest, although overall test-retest reliability is high [25
]. Changes on the DGI may be related to vestibular compensation [26
Obstacle avoidance is an important component of many mobility skills. Older adults generally perform worse than younger adults on obstacle avoidance tests [27
]. Normals undergoing visuomotor and vestibulomotor adaptation perform poorly on obstacle avoidance tasks [30
]. Obstacle avoidance during treadmill walking has been shown to be sensitive to change in fallers after a falls prevention program although a standing balance test showed no change [33
]. Not surprisingly, the DGI includes an obstacle avoidance subtest. The first goal of the present study was to test the usefulness of our previously developed Functional Mobility Test (FMT) obstacle avoidance task [31
] as a test of locomotor balance.
The literature does not indicate which test or combination of tests best identifies patients with balance disorders or best predicts which patients have vestibular impairments. Most studies have examined falls prediction. Vestibular disorders have complex manifestations so a combination of tests that measure different factors may be more useful for screening than a single test [6
] . Since standing and walking are different skills, a combination of tests of standing and walking may be most accurate in predicting patients with balance impairments.
The second goal of the present study was to determine which test or combination of tests would be best for screening people for vestibular disorders. Such screening tests could be used by health care providers who are not physicians, to help identify individuals who might benefit from referral to a physician who has expertise in diagnosis of vestibular disorders. Such tests might also be useful in population-based epidemiologic screening studies that require inexpensive but valid and reliable screening tests to approximate the incidence and prevalence of vestibular disorders in various populations. Aside from FMT, which we developed, we selected tests because they are common, normed, clinical tests; easy to administer; easy to score and easy to interpret.