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Reliability and Validity of Trunk Assessment for People With Multiple Sclerosis

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

 
Background and Purpose. Standardized scales are a prerequisite for rehabilitation and research. This study was designed to determine the reliability and validity of scores on items of the trunk assessment of the Melsbroek Disability Scoring Test (MDST) and Trunk Impairment Scale (TIS) in people with multiple sclerosis (MS).

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

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

 
The trunk plays a critical role in the organization of postural reactions. For a variety of functional tasks, trunk segment displacement without loss of balance is of crucial importance.^1,2 Balance and transfer skills are significantly related to falls in people with multiple sclerosis (MS).³

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.^9–11 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

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

 
Subjects

Participants in the study were recruited from the National Multiple Sclerosis Center of Melsbroek, Belgium. The center offers a multidisciplinary rehabilitation program for people with MS. People attending the treatment program have a wide variety of common MS symptoms, and their mobility ranges from being ambulatory to being bound to an electric wheelchair. Rehabilitation services are provided for hospitalized patients as well as outpatients. All people with a definite diagnosis of MS who gave written informed consent were eligible for participation. Subjects were excluded from the study if they had orthopedic, cognitive, or behavioral problems that could interfere with the testing procedure. Thirty consecutive people with MS (15 women, 15 men) with a mean age (±SD) of 53±10.3 years and a mean disease duration (±SD) of 16±8.1 years participated in the study.

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 Test–Trunk 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 subject’s 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

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

 
The participants’ median total FIM score was 85 points (range=43–110), indicating dependency for some to several activities of daily living. The median EDSS score for the 30 people with MS was 7.5 (range=5.5–8.5), indicating impairments in several functional systems and mild to severe ambulatory problems.

The Melsbroek Disability Scoring Test–Trunk 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%.

View larger version (7K): [in this window] [in a new window] Figure 1. Bland-Altman plot of the total range of differences of total scores for the trunk assessment of the Melsbroek Disability Scoring Test (IRDIFF) against the total range of mean scores (IRMEAN) for interrater agreement. The solid line represents the mean of the differences. The dashed lines define the limits of agreement (mean of the difference±2 SD). The value next to each bullet indicates the number of subjects at that position. A bullet with no value implies that only one subject is present at that position.

View larger version (7K): [in this window] [in a new window] Figure 2. Bland-Altman plot of the total range of differences of total scores for the trunk assessment of the Melsbroek Disability Scoring Test (TRDIFF) against the total range of mean scores (TRMEAN) for test-retest agreement. The solid line represents the mean of the differences. The dashed lines define the limits of agreement (mean of the difference±2 SD). The value next to each bullet indicates the number of subjects at that position. A bullet with no value implies that only one subject is present at that position.

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).

View larger version (6K): [in this window] [in a new window] Figure 3. Bland-Altman plot of the total range of differences of total Trunk Impairment Scale scores (IRDIFF) against the total range of mean scores (IRMEAN) for interrater agreement. The solid line represents the mean of the differences. The dashed lines define the limits of agreement (mean of the difference±2 SD). The value next to each bullet indicates the number of subjects at that position. A bullet with no value implies that only one subject is present at that position.

View larger version (6K): [in this window] [in a new window] Figure 4. Bland-Altman plot of the total range of differences of total Trunk Impairment Scale scores (TRDIFF) against the total range of mean scores (TRMEAN) for test-retest agreement. The solid line represents the mean of the differences. The dashed lines define the limits of agreement (mean of the difference±2 SD). The value next to each bullet indicates the number of subjects at that position. A bullet with no value implies that only one subject is present at that position.

	Discussion

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

 
The aim of our study was to investigate the reliability and validity of scores on items of the trunk assessment of the MDST and the TIS for people with MS. All weighted kappa values for the trunk assessment of the MDST were .74 or higher. All except 3 items of the TIS showed kappa and weighted kappa values of .60 or higher. Two items with kappa values below .60 assessed compensation strategies during lateral flexion movements of the trunk. The other items of the dynamic sitting balance subscale that assess compensation strategies (items 3 and 10) also showed rather low kappa values. Similar results were found when evaluating the TIS in people who had a stroke.¹⁵ A better definition of the possible compensation strategies when performing the TIS could be considered.

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 observer’s 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,^28–30 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

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

 
Our study was designed to determine the reliability and validity of scores on items of the trunk assessment of the MDST and the TIS for people with MS. Interrater and test-retest agreement for the different items, the subscale scores, and total scores were highly acceptable. Construct validity of both trunk tests was established. Because trunk performance is directly related to disability, measuring the trunk is important in the examination and treatment of people with MS. Future research should evaluate additional psychometric properties of the new instruments and examine the role of the trunk in the rehabilitation and prognosis of people with MS.

	Appendix 1

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

 

View larger version (47K): [in this window] [in a new window] The Melsbroek Disability Scoring Test—Trunk Assessment

	Appendix 2

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

View larger version (58K): [in this window] [in a new window]

	Footnotes

 
Mr Verheyden, Dr Nuyens, Dr Nieuwboer, and Dr De Weerdt provided concept/idea/research design and data analysis. Mr Verheyden and Dr Nuyens provided writing and data collection. Dr Nuyens, Dr Nieuwboer, Mr Van Asch, Dr Ketelaer, and Dr De Weerdt provided project management. Dr Nuyens and Mr Van Asch provided subjects. Mr Van Asch and Dr Ketelaer provided facilities/equipment. Dr Ketelaer provided institutional liaisons. Dr Nieuwboer, Mr Van Asch, Dr Ketelaer, and Dr De Weerdt provided consultation (including review of manuscript before submission).

This study was approved by the Ethical Commission of the Medical Faculty of the Katholieke Universiteit Leuven.

	References

Top Abstract Introduction Method Results Discussion Conclusion Appendix 1 Appendix 2 References

 

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This Article Abstract Full Text (PDF) 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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Verheyden, G. Articles by De Weerdt, W. Search for Related Content PubMed PubMed Citation Articles by Verheyden, G. Articles by De Weerdt, W.