Gait & Posture 39 (2014) 670
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Reply to Letter to the Editor Re: Letter to the Editor by Cameron et al. Dear Editor, We’d like to thank Dr. Cameron and her colleagues for their letter in response to our article ‘‘Balance impairment in people with multiple sclerosis: Preliminary evidence for the Balance Evaluation Systems Test’’ [1]. As identified in our title and in the article’s text, our study was a preliminary validation that required further confirmation. Cameron et al. provide a thorough dataset of a much larger cohort while also extending their analysis from the original BESTest to the more clinically feasible mini-BESTest. We appreciate seeing that their results confirm our preliminary findings and further validate the mini-BESTest as a correlate to additional instrumented and clinical measures of balance impairment. Cameron et al., however, note that the mini-BESTest did not significantly identify people with and without a fall history or prospectively identify future falls. Cameron et al. speculate that differences may relate to the content of the exams themselves (the mini-BESTest does not assess mechanical constraints or limits of stability) or to differences in the study populations. Our study population included only 13 people with predominantly mild-tomoderate, relapse-remitting multiple sclerosis (MS). Given the larger study population of Cameron et al., we are curious whether this population included other sub-types of MS and if they tested a wider range of disease severity. If so, the lack of correlation may reflect a non-linear function between falls and balance impairment. Specifically, falls may increase with increasing balance impairment at mild-to-moderate levels of impairment, whereas falls may decrease with more severe impairments because declines in risk behaviors and activity levels sharply decrease the potential for experiencing falls for people with more disabling symptoms. If, however, such a difference in populations does not explain the lack of correlations between the mini-BESTest and fall risk, then we offer the following insights regarding differences between the original and mini versions of the BESTest. We recently tested the brief-BESTest as a novel, shortened version of the original BESTest that, unlike the mini-BESTest, includes all contexts of postural control as the original BESTest, but only includes the one
0966-6362/$ – see front matter ß 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gaitpost.2013.10.007
item per context that (in our cohort) most explained its associated section score [2]. Again, the cohort was small, but we found evidence to suggest that tests of mechanical constraints and limits of stability are important components for identifying fall risk in people with MS – a finding that we also identified in a separate prospective falls study on a large cohort using instrumented measures of balance and gait [2,3]. Although the mini-BESTest in our small cohort still significantly identified people with MS who reported a recent fall history (unlike Cameron et al.), its sensitivity was not as high as either the original BESTest or brief-BESTest, which contain items that represent all six suggested contexts of postural control. Thus, as suggested by Cameron et al., limitations of the mini-BESTest may contribute to its relatively lower sensitivity to previous or prospective falls in people with MS. Nevertheless, it is encouraging that comprehensive clinical exams of balance and gait are available to identify balance impairments in people with MS, and that all versions of the BESTest appear valid when compared to instrumented tests of balance and gait. Conflict of interest None. References [1] Jacobs JV, Kasser SL. Balance impairment in people with multiple sclerosis: preliminary evidence for the balance evaluation systems test. Gait Posture 2012;36:414–8. [2] Padgett PK, Jacobs JV, Kasser SL. Is the BESTest at its best?. A suggested brief version based on inter-rater reliability, validity, internal consistency, and theoretical construct. Phys Ther 2012;92:1197–207. [3] Kasser SL, Jacobs JV, Foley JT, Cardinal BJ, Maddalozzo GF. A prospective evaluation of balance, gait, and strength to predict falling in women with multiple sclerosis. Arch Phys Med Rehabil 2011;92:1840–6.
Jesse V. Jacobs Susan L. Kasser Department of Rehabilitation and Movement Science, College of Nursing and Health Sciences, University of Vermont, United States E-mail address: [email protected] (J.V. Jacobs)
Contents lists available at ScienceDirect
Gait & Posture journal homepage: www.elsevier.com/locate/gaitpost
Reply to Letter to the Editor Re: Letter to the Editor by Cameron et al. Dear Editor, We’d like to thank Dr. Cameron and her colleagues for their letter in response to our article ‘‘Balance impairment in people with multiple sclerosis: Preliminary evidence for the Balance Evaluation Systems Test’’ [1]. As identified in our title and in the article’s text, our study was a preliminary validation that required further confirmation. Cameron et al. provide a thorough dataset of a much larger cohort while also extending their analysis from the original BESTest to the more clinically feasible mini-BESTest. We appreciate seeing that their results confirm our preliminary findings and further validate the mini-BESTest as a correlate to additional instrumented and clinical measures of balance impairment. Cameron et al., however, note that the mini-BESTest did not significantly identify people with and without a fall history or prospectively identify future falls. Cameron et al. speculate that differences may relate to the content of the exams themselves (the mini-BESTest does not assess mechanical constraints or limits of stability) or to differences in the study populations. Our study population included only 13 people with predominantly mild-tomoderate, relapse-remitting multiple sclerosis (MS). Given the larger study population of Cameron et al., we are curious whether this population included other sub-types of MS and if they tested a wider range of disease severity. If so, the lack of correlation may reflect a non-linear function between falls and balance impairment. Specifically, falls may increase with increasing balance impairment at mild-to-moderate levels of impairment, whereas falls may decrease with more severe impairments because declines in risk behaviors and activity levels sharply decrease the potential for experiencing falls for people with more disabling symptoms. If, however, such a difference in populations does not explain the lack of correlations between the mini-BESTest and fall risk, then we offer the following insights regarding differences between the original and mini versions of the BESTest. We recently tested the brief-BESTest as a novel, shortened version of the original BESTest that, unlike the mini-BESTest, includes all contexts of postural control as the original BESTest, but only includes the one
0966-6362/$ – see front matter ß 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gaitpost.2013.10.007
item per context that (in our cohort) most explained its associated section score [2]. Again, the cohort was small, but we found evidence to suggest that tests of mechanical constraints and limits of stability are important components for identifying fall risk in people with MS – a finding that we also identified in a separate prospective falls study on a large cohort using instrumented measures of balance and gait [2,3]. Although the mini-BESTest in our small cohort still significantly identified people with MS who reported a recent fall history (unlike Cameron et al.), its sensitivity was not as high as either the original BESTest or brief-BESTest, which contain items that represent all six suggested contexts of postural control. Thus, as suggested by Cameron et al., limitations of the mini-BESTest may contribute to its relatively lower sensitivity to previous or prospective falls in people with MS. Nevertheless, it is encouraging that comprehensive clinical exams of balance and gait are available to identify balance impairments in people with MS, and that all versions of the BESTest appear valid when compared to instrumented tests of balance and gait. Conflict of interest None. References [1] Jacobs JV, Kasser SL. Balance impairment in people with multiple sclerosis: preliminary evidence for the balance evaluation systems test. Gait Posture 2012;36:414–8. [2] Padgett PK, Jacobs JV, Kasser SL. Is the BESTest at its best?. A suggested brief version based on inter-rater reliability, validity, internal consistency, and theoretical construct. Phys Ther 2012;92:1197–207. [3] Kasser SL, Jacobs JV, Foley JT, Cardinal BJ, Maddalozzo GF. A prospective evaluation of balance, gait, and strength to predict falling in women with multiple sclerosis. Arch Phys Med Rehabil 2011;92:1840–6.
Jesse V. Jacobs Susan L. Kasser Department of Rehabilitation and Movement Science, College of Nursing and Health Sciences, University of Vermont, United States E-mail address: [email protected] (J.V. Jacobs)
