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Invited Commentary

SA Studenski, MD, MPH, is Professor, Department of Medicine (Geriatrics), University of Pittsburgh, and Staff Physician, VA Pittsburgh GRECC, 3471 Fifth Ave, Suite 500, Pittsburgh, PA 15213 (USA)

Address all correspondence to Dr Studenski at: sas33{at}pitt.edu

In their article,¹ Muir et al present new evidence for the application of likelihood ratios to estimate fall risk with a multilevel form of the Berg Balance Scale (BBS). This is an important new contribution to the field. Although several investigators^2,3 have calculated likelihood ratios for recurrent falls, Muir et al are the first to expand their use to a multilevel format. Multiple interpretable levels of a test make sense to clinicians. They understand from experience that tests are often much more than just positive or negative; they might be really positive, just a little positive, or even equivocal. Thus, Muir et al take us to a clinically rational next step by providing greater discrimination across the range of scores. We now can define a group at marked increased risk for recurrent falls: those with BBS scores of 40. This cutoff score is associated with a positive likelihood ratio of more than 5, suggesting a moderately powerful predictive capacity. This study also further reinforces the painful fact any one screening maneuver has only relatively modest explanatory power to predict any kind of fall-related outcome. Muir et al present convincing evidence that even a test as good as the BBS—although helpful—cannot reach expected standards for a very good screening test by itself.

So what are the next steps? Perhaps these new findings could be tested as part of a diagnostic sequence, as recommended in the Guideline for the Prevention of Falls in Older Persons.⁴ It might be informative to estimate the pretest odds of becoming a recurrent faller, based on initial categories of fall history: no falls, a single fall, or multiple falls in the prior year. The new BBS likelihood ratio estimates then could be applied to derive posttest odds and used to make reasonable clinical decisions. For example, it may be that older people with a history of recurrent falls have such high pretest odds of recurrence that any BBS score cannot really alter the posttest odds enough to change care decisions. Perhaps the groups whose care plan might change the most are those at intermediate pretest odds of recurrent falls: those with a single prior fall or those with no fall history but with complaints of unsteadiness.⁴

Negative tests also can be very useful. Clearly negative tests can reassure patients and providers that risk appears to be low. Muir et al did not formally report negative likelihood ratios, which can be used to identify very low probability of an outcome. My informal calculations, based on the data provided in the tables, suggest that there are no levels of the BBS that yield negative likelihood ratios under 0.5 or so. With no level of BBS score associated with a very low likelihood of falls, there is no score that can reduce the pretest odds of falls enough to be useful clinically as a negative result. An implication for future research would be that balance scales be used to identify low risk for falls should be expanded to include some very difficult items that might better predict excellent balance and those individuals with the lowest risk for future falls.⁵

This work also is a compelling reminder to me of the invaluable contributions made by the field of physical therapy to the care of older adults. Physical therapy has given the world numerous outstanding leaders whose groundbreaking work affects older people every day. Some of the physical therapists who, in my opinion, have made a difference are Katherine Berg for her work on balance and falls,^6–8 Anne Shumway-Cook for her work on balance and mobility,^9–12 Faye Horak for her work on balance and falls,^13–15 Alan Jette for his work on measuring disability,^16–19 Steve Wolf for his work on tai chi,^20–22 and Pamela Duncan for her work on balance and on stroke.^23–26 I offer my thanks to the field of physical therapy for imparting its knowledge to these wonderful people and to these individuals for sharing their knowledge with all of us.

The discipline of physical therapy offers a specialized knowledge base, set of clinical skills, and way of thinking that are desperately needed to continue to improve the lives of older people. As an "ambassador" from the discipline of geriatric medicine, I welcome young and experienced physical therapists to join with us in mutually beneficial collaboration on behalf of more good years for the older people of today and then later for ourselves, when we eventually, inevitably, join their ranks.

	References

 

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2. Ganz DA, Bao Y, Shekelle PG, Rubenstein LZ. Will my patient fall? JAMA. 2007;297:77–86.[Abstract/Free Full Text]
3. Riddle DL, Stratford PW. Interpreting validity indexes for diagnostic tests: an illustration using the Berg Balance Test. Phys Ther. 1999;79:939–948.[Abstract/Free Full Text]
4. American Geriatrics Society, British Geriatrics Society, and American Academy of Orthopaedic Surgeons Panel on Falls Prevention. Guideline for the prevention of falls in older persons. J Am Geriatr Soc. 2001;49:664–672.[CrossRef][Web of Science][Medline]
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8. Berg KO, Wood-Dauphinée SL, Williams JI, Maki B. Measuring balance in the elderly: validation of an instrument. Can J Public Health. 1992;83(suppl 2):S7–S11.[Web of Science][Medline]
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11. Shumway-Cook A, Woollacott M. Attentional demands and postural control: the effect of sensory context. J Gerontol A Biol Sci Med Sci. 2000;55:M10–M16.[Web of Science][Medline]
12. Shumway-Cook A, Woollacott M, Kerns KA, Baldwin M. The effects of two types of cognitive tasks on postural stability in older adults with and without a history of falls. J Gerontol A Biol Sci Med Sci. 1997;52:M232–M240.
13. Horak FB. Postural orientation and equilibrium: what do we need to know about neural control of balance to prevent falls? Age Ageing. 2006;35(suppl 2):ii7–ii11.[Abstract/Free Full Text]
14. Horak FB, Shupert CL, Mirka A. Components of postural dyscontrol in the elderly: a review. Neurobiol Aging. 1989;10:727–738.[CrossRef][Web of Science][Medline]
15. Shumway-Cook A, Horak FB. Assessing the influence of sensory interaction of balance: suggestion from the field. Phys Ther. 1986;66:1548–1550.[Abstract/Free Full Text]
16. Haley SM, Jette AM, Coster WJ, et al. Late Life Function and Disability Instrument, II: development and evaluation of the function component. J Gerontol A Biol Sci Med Sci. 2002;57:M217–M222.[Web of Science][Medline]
17. Jette AM, Haley SM, Coster WJ, et al. Late life function and disability instrument, I: development and evaluation of the disability component. J Gerontol A Biol Sci Med Sci. 2002;57:M209–M216.[Web of Science][Medline]
18. Keysor JJ, Jette AM. Have we oversold the benefit of late-life exercise? J Gerontol A Biol Sci Med Sci. 2001;56:M412–M423.[Web of Science][Medline]
19. Lachman ME, Howland J, Tennstedt S, et al. Fear of falling and activity restriction: the Survey of Activities and Fear of Falling in the Elderly (SAFE). J Gerontol B Psychol Sci Soc Sci. 1998;53:P43–P50.
20. Wolf SL, Barnhart HX, Ellison GL, Coogler CE. The effect of Tai Chi Quan and computerized balance training on postural stability in older subjects. Atlanta FICSIT Group. Frailty and Injuries: Cooperative Studies on Intervention Techniques. Phys Ther. 1997;77:371–381; discussion 382–384.[Abstract/Free Full Text]
21. Wolf SL, Barnhart HX, Kutner NG, et al. Reducing frailty and falls in older persons: an investigation of Tai Chi and computerized balance training. Atlanta FICSIT Group. Frailty and Injuries: Cooperative Studies of Intervention Techniques. J Am Geriatr Soc. 1996;44:489–497.[Web of Science][Medline]
22. Wolf SL, Sattin RW, Kutner M, et al. Intense tai chi exercise training and fall occurrences in older, transitionally frail adults: a randomized, controlled trial. J Am Geriatr Soc. 2003;51:1693–1701.[CrossRef][Web of Science][Medline]
23. Duncan PW, Studenski SA, Richards L, et al. Randomized clinical trial of therapeutic exercise in subacute stroke. Stroke. 2003;34:2173–2180.[Abstract/Free Full Text]
24. Duncan PW, Chandler JM, Studenski SA, et al. How do physiological components of balance affect mobility in elderly men? Arch Phys Med Rehabil. 1993;74:1343–1349.[CrossRef][Web of Science][Medline]
25. Duncan PW, Studenski SA, Chandler JM, Prescott B. Functional reach: predictive validity in a sample of elderly male veterans. J Gerontol. 1992;47:M93–M98.[Abstract]
26. Duncan PW, Weiner DK, Chandler JM, Studenski SA. Functional reach: a new clinical measure of balance. J Gerontol. 1990;45:M192–M197.[Abstract]

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This Article Extract Full Text (PDF) Correction (v88,p688) Submit a response Alert me when this article is cited Alert me when Rapid Responses are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Studenski, S. A Search for Related Content PubMed PubMed Citation Articles by Studenski, S. A Related Collections Balance Tests and Measurements Falls and Falls Prevention Social Bookmarking                      What's this?