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Research Reports |
G Verheyden, PT, is Research Assistant, Department of Rehabilitation Sciences, Katholieke Universiteit Leuven, Tervuursevest 101, 3001 Leuven, Belgium
G Nuyens, PT, PhD, is Research Physiotherapist, Department of Rehabilitation Sciences, Katholieke Universiteit Leuven, and Physiotherapist, National Multiple Sclerosis Center, Melsbroek, Belgium
A Nieuwboer, PT, PhD, is Professor, Department of Rehabilitation Sciences, Katholieke Universiteit Leuven
P Van Asch, PT, is Head of Physiotherapy, National Multiple Sclerosis Center, Melsbroek
P Ketelaer, MD, is former Medical Director, National Multiple Sclerosis Center, Melsbroek
W De Weerdt, PT, PhD, is Professor, Department of Rehabilitation Sciences, Katholieke Universiteit Leuven
(geert.verheyden{at}faber.kuleuven.be). Address all correspondence to Mr Verheyden
Submitted February 18, 2005;
Accepted June 1, 2005
| Abstract |
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Subjects. Thirty people with MS participated in the study.
Methods. Interrater and test-retest reliability and construct validity were assessed.
Results. Kappa and weighted kappa values for the items of the trunk assessment of the MDST ranged from .74 to .95, and the kappa and weighted kappa values for the TIS items ranged from .46 to 1.00. Intraclass correlation coefficients for interrater and test-retest agreement were .93 and .92, respectively, for the trunk assessment of the MDST and .97 and .95, respectively, for the TIS. Bland-Altman analysis showed consistency of scores without observer bias. Construct validity was established.
Discussion and Conclusion. The MDST and TIS provide reliable assessments of the trunk and are valid scales for measuring trunk performance in people with MS. [Verheyden G, Nuyens G, Nieuwboer A, et al. Reliability and validity of trunk assessment for people with multiple sclerosis.
Key Words: Multiple sclerosis Outcome assessment Rehabilitation Reproducibility of results
| Introduction |
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A frequently occurring problem in MS is postural incompetence, which is often associated with paresis and proprioceptive, cerebellar, or vestibular impairments.4 Postural disturbances in sitting not only affect limb mobility but induce other secondary problems, such as pain, sphincter problems, and decubitus, in people with MS who have severe disabilities.5,6 Instability in sitting is related to malalignment of body segments and may eventually compromise respiratory function and cause difficulties in speech and swallowing.7
During activities of daily living, proper functioning of the trunk depends on a variety of interacting factors. Problems at the level of impairment, such as loss of muscle strength and mobility or an increase or decrease in muscle tone, can reflect in the functional performance of the trunk.8 Several scales to examine people with MS are reported.911 To the best of our knowledge, a standardized clinical tool to measure trunk performance is not available for people with MS.
The Trunk Control Test, a standardized measure with good psychometric properties, has been available since 1990 for use with people who have had a stroke.12 The Trunk Control Test, however, does not take the quality of trunk movement (eg, appropriate shortening and lengthening of the trunk, selective movements of the upper and lower parts of the trunk, moving the trunk without compensations) into account.12 The Trunk Control Test has a moderate correlation with trunk strength when measured with a handheld dynamometer (Spearman rank correlation coefficients=.32.50).13 Furthermore, the sensitivity of the scores of the Trunk Control Test over time is questioned in patients with a chronic history of stroke.14
In the National Multiple Sclerosis Center of Melsbroek, Belgium, the Melsbroek Disability Scoring Test (MDST) is used to assess the overall disability of people with MS. One of the subtests assesses trunk performance. So far, no psychometric analysis of the MDST has been reported for the scale as a whole or for the trunk subtest.
Recently, the Trunk Impairment Scale (TIS) was developed to measure motor impairment of the trunk after stroke.15 The test assesses static and dynamic sitting balance and trunk coordination. Psychometric properties of the TIS for people after stroke were reported previously.15 The use of the TIS with people with MS seems justified because clinical impairments of the trunk such as paresis or changes in muscle tone are present in people with MS as well as in patients after stroke. It was the aim of our study to examine the interrater and test-retest reliability and construct validity of scores on items of the trunk assessment of the MDST and the TIS in people with MS.
| Method |
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Procedure
After providing informed consent, subjects were evaluated in a sitting position on a plinth. Trunk examination was carried out on the basis of 2 tests, the trunk assessment of the MDST and the TIS. The order of the 2 trunk tests was randomized. Two physical therapists with several years of experience in the field of neurological rehabilitation examined all subjects together but scored them independently. Comparison of their results was used to determine interrater agreement. In addition, one of the physical therapists, who worked at the National Multiple Sclerosis Center, examined every subject alone before or after the day of interrater observation to assess test-retest agreement. Subjects were examined at the same time of the day to avoid the impact of fatigue or rehabilitation activities on trunk performance. Whether the subjects were examined on the previous day or the next day when assessing test-retest agreement was randomized as well.
The Melsbroek Disability Scoring TestTrunk Assessment (Appendix 1)
The MDST was developed at the National Multiple Sclerosis Center of Melsbroek, Belgium, to investigate disability in people with MS. Trunk performance is assessed as part of a more comprehensive examination. The trunk assessment part of the MDST contains 4 items. Static balance is assessed by asking the subject to remain in the sitting position while applying manual pressure to the sternum, thoracic spine, and both sides of the body. Dynamic balance in the sagittal plane is assessed by asking the subject to move the trunk as far forward and backward as possible without losing balance. For dynamic balance in the frontal plane, the subject is asked to move as much weight as possible to the left and right sides. Each item is scored on a 4-point ordinal scale. The total score for the trunk assessment of the MDST ranges from 0 for a perfect performance to 60 for a minimal performance; therefore, a lower score indicates a better trunk performance.
The Trunk Impairment Scale for People With MS (Appendix 2)
The TIS assesses static and dynamic sitting balance and trunk coordination in a sitting position. The static subscale investigates the ability of the subject to maintain the sitting position with the feet supported, while the legs are passively crossed and when the subject crosses the legs actively. Subjects who had a stroke crossed the nonhemiplegic leg over the hemiplegic leg. Subjects with MS crossed the strongest leg over the weakest leg. The strongest leg was identified by asking the subject to lift the knee against manual resistance of the therapist. If no difference was found, the subjects side of preference was used for crossing the legs.
The dynamic subscale contains items on lateral flexion of the trunk and unilateral lifting of the hip. To assess the coordination of the trunk, the subject is asked to rotate the upper or lower part of the trunk 6 times, initiating the movements either from the shoulder girdle or from the pelvic girdle, respectively. For each item, a 2-, 3-, or 4-point ordinal scale is used. On the static and dynamic sitting balance and coordination subscales, the maximal scores that can be reached are 7, 10, and 6 points, respectively. The total score for the TIS ranges between 0 for a minimal performance to 23 for a perfect performance, with a higher score indicating a better trunk performance. Both the MDST and TIS were designed to assess characteristics of trunk movement that may be important for activities of daily living.
Finally, the subjects were examined using the Functional Independence Measure (FIM)16 and the Extended Disability Status Scale (EDSS).17 The FIM is a reliable, valid, and responsive continuous measure of disability and evaluates the level of assistance required to perform several activities of daily living on a scale from 18 (totally dependent) to 124 (normal status).18 The ordinal EDSS is a reliable and valid measure of impairment and disability. It assesses disease severity and the ability to ambulate, to use the upper limbs, and to communicate and swallow on a scale from 0 (normal status) to 10 (death due to MS).18
Data Analysis
The interrater and test-retest reliability of scores on individual test items of the trunk assessment of the MDST and TIS were assessed using the kappa statistic (for dichotomous items), the weighted kappa statistic (for ordinal items), and the percentage of agreement. Reliability was considered acceptable when the kappa or weighted kappa statistic was .60 or higher.19
The reliability of total test scores for the trunk assessment of the MDST and TIS (subscale totals and total score) was assessed using intraclass correlation coefficients (ICC[1,1]).20 Reliability was considered to be good when the ICC was .80 or higher.21 A standard error of measurement was calculated to determine consistency of measurements in absolute terms. Furthermore, the consistency of measurements was verified graphically using the method of Bland and Altman.22 This method plots differences between 2 measurements against the average of the 2 measurements. Size and range of differences, scoring distribution, and possible measurement bias can be visually assessed. The mean difference between measurements and the 95% confidence intervals for the mean difference between measurements for interrater and test-retest agreement were calculated according to the procedure described by Rankin and Stokes.23 Construct validity was determined on the basis of Spearman rank correlation coefficients by comparing the trunk assessment of the MDST and TIS scores with the FIM and EDSS scores of the participants with MS.
| Results |
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The Melsbroek Disability Scoring TestTrunk Assessment
Weighted kappa statistic values for the interrater and test-retest agreement for the 4 items of the trunk assessment of the MDST are listed in Table 1. Values for interrater reliability ranged from .76 to .95. Values for test-retest agreement were between .74 and .90. All percentages of agreement exceeded 72%.
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The Trunk Impairment Scale for People With MS
The kappa and weighted kappa values for the individual test items varied between .87 and 1.00 for the static sitting balance subscale of the TIS, between .49 and 1.00 for the dynamic sitting balance subscale, and between .46 and .82 for the coordination subscale of the TIS (Tab. 3). The dynamic sitting balance subscale showed the lowest kappa values, .49 and .55, for the observation of compensation strategies during trunk movements. A kappa value of .46 was found in the coordination subscale when observing the rotation of the lower part of the trunk (pelvic girdle). All percentages of agreement for the individual items of the TIS were between 70% and 100% (Tab. 3).
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| Discussion |
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The third item with a weighted kappa value below .60 was item 3 of the coordination subscale, which scores the symmetry of rotating the pelvic girdle. As in the study of the reliability of scores on the TIS in people after stroke by Verheyden et al,15 the items of the coordination subscale showed lower weighted kappa values than the items for static and dynamic sitting balance. This result is in line with the lower reliability values found in the study of Nieuwboer et al24 when observing symmetry of sitting balance after stroke. These results suggest that developing a scoring system to evaluate the symmetry of a posture or movement is difficult to achieve and might depend on parameters such as the observers experience.
The weighted kappa values of the above-mentioned items of the TIS in our study were below the suggested value of .60; however, the low kappa values were combined with high percentages of agreement. This often indicates a skewed distribution of scores for these particular items. In such cases, the literature reports that the kappa or weighted kappa statistic may not be appropriate to assess reliability.25,26 For the items in question, substantial percentages of agreement (between 70% and 87%) were found that could justify the further inclusion of these items in the TIS for people with MS.
Intraclass correlation coefficients for interrater and test-retest agreement for the trunk assessment of the MDST were .93 and .92, respectively. The reported ICCs for the subscales of the TIS and total TIS score ranged from .82 to .98. These values are comparable to the ICC values obtained when using the TIS to evaluate people who have had a stroke.15 The method of Bland and Altman was used in addition to the ICC values because neither test alone provides sufficient reliability information.23 Another indication for good interrater and test-retest agreement is that the mean differences were relatively close to 0. Only 2 subjects were outside the limits of agreement both for interrater and test-retest agreement for the 2 trunk tests.
The smaller differences found for the low and high ranges of the means of the total TIS score indicates a higher agreement in people with severe or minimal impairments in trunk performance, respectively. The larger differences in the middle range suggest that it is more difficult to examine people with MS with a moderate trunk performance. The plots of the total range of differences for both trunk tests support the reliability of the assessments throughout the full range of scores. In addition, the 95% confidence interval for the mean difference between the 2 trunk tests indicates that no bias exists between the 2 observations because 0 lies within the interval.27 The low standard error of measurement of both trunk scales for the interrater and test-retest agreement indicates further consistency of scores. However, the design used to assess interrater and test-retest reliability prohibits generalizability of the results and is therefore a limitation of the study.
Both trunk assessment tools appeared to be easy to administer. The TIS took no more than 10 minutes to complete, which was comparable to what was found for people who have had a stroke.15 No comparative values for the trunk assessment of the MDST are available, but the testing protocol never exceeded 10 minutes.
In people with stroke, crossing the legs in the static sitting balance subscale was performed only with the unaffected leg over the affected leg.15 For people with MS, this test item was modified by crossing the strongest leg over the weakest leg. The underlying idea behind this test item is to evaluate the trunk strategies used to complete the task and not to evaluate whether the patient can cross the legs. Future research should further explore the effect on trunk performance of crossing the strongest or weakest leg. Other psychometric properties, such as predictive validity and responsiveness, of both the trunk assessment of the MDST and the TIS should be evaluated as well.
The wide range of scores on both trunk scales shows that trunk performance is impaired in a substantial number of people with MS. High correlations between both trunk test scores and the total FIM and EDSS scores suggest a close relationship between trunk performance and functional disability in people with MS. Future studies should clarify whether trunk rehabilitation, as recommended in several rehabilitation approaches for people with neurological conditions,2830 is justified for people with MS and improves overall functional performance.
When considering the use of the trunk assessment of the MDST or the TIS to assess trunk performance of people with MS, the final goal of the examination must be considered. The trunk assessment of the MDST is part of a more comprehensive test that is used in the National Multiple Sclerosis Center of Melsbroek. The total test was designed to evaluate overall disability in people with MS. With only 4 trunk items, the scope of measurement is limited and largely addresses sitting balance. It also has a larger ceiling effect. Only 3% of the participants in our study achieved the maximum score on the TIS compared with 13% who obtained a maximum score on the trunk assessment of the MDST. The Bland-Altman plots support a possible ceiling effect when looking at the distribution of scores on the trunk assessment of the MDST. They are skewed toward the lower part of the scale, indicating a better trunk performance. The distribution of scores on the TIS is more even over the total range of the scale.
The TIS assesses coordination as well as static and dynamic sitting balance. The items of the TIS are more directly linked to treatment of the trunk in preparation of functional movements. A recent study31 showed that patients who have had a stroke use the upper part of the trunk far more than the lower part during reaching tasks. This finding justifies a differential examination of the upper and lower parts of the trunk. The static and dynamic sitting balance subscale of the TIS assess movements in the sagittal and frontal planes; the coordination subscale also scores movements in the horizontal plane. The importance of axial rotation during activities of daily living suggests the necessity of assessing rotation when evaluating trunk performance.32,33
| Conclusion |
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| Appendix 1 |
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| Appendix 2 |
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| Footnotes |
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This study was approved by the Ethical Commission of the Medical Faculty of the Katholieke Universiteit Leuven.
| References |
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This article has been cited by other articles:
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N. M Kayes, P. J Schluter, K. M McPherson, D. Taylor, and G. S Kolt The Physical Activity and Disability Survey -- Revised (PADS-R): an evaluation of a measure of physical activity in people with chronic neurological conditions Clinical Rehabilitation, June 1, 2009; 23(6): 534 - 543. [Abstract] [PDF] |
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G. Verheyden, A. Nieuwboer, A. Van de Winckel, and W. De Weerdt Clinical tools to measure trunk performance after stroke: a systematic review of the literature Clinical Rehabilitation, May 1, 2007; 21(5): 387 - 394. [Abstract] [PDF] |
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