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NDT Advance Access originally published online on July 4, 2007
Nephrology Dialysis Transplantation 2007 22(11):3318-3321; doi:10.1093/ndt/gfm454
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© The Author [2007]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org


The ‘Sit-to-Scale’ score—a pilot study to develop an easily applied score to follow functional status in elderly dialysis patients

G. Kenzo Saito1 and Sarbjit Vanita Jassal1,2

1Division of Nephrology, University Health Network and 2Toronto Rehabilitation Institute, Toronto Canada

Correspondence and offprint requests to: Dr S. V. Jassal, Dialysis Rehabilitation Program, Toronto Rehabilitation Institute, Staff Physician, Univ Health Network, 8NU-857, 200 Elizabeth St, Toronto, M5G 2C4, Canada. Email: vanita.jassal{at}uhn.on.ca

Keywords: disability; elderly; gait speed; geriatrics; haemodialysis



   Introduction
Top
 Introduction
Subjects and methods
 Results
 Discussion
 References
 
In Canada, the number of older persons requiring treatment for end-stage renal disease (ESRD) rose by nearly 20% between 1997 and 2001 [1]. Fifty-five percent of all new dialysis patients are 65 years of age and older, and almost 25% are 75 years and older [2]. Similar demographic trends have been observed in the United States and the United Kingdom [3,4]. Cross-sectional studies have shown older haemodialysis patients are generally less active and more physically impaired than younger patients [3,5,6]. In addition older dialysis patients suffer from a high degree of disability and functional dependence [6–9]. Functional impairment is important, clinically, for many reasons. In the general population, functional impairment predicts falls, fractures and hospitalization [10–12]. In the dialysis population clinical outcomes such as falls or fractures are very common, with studies suggesting that over 45% of older dialysis patients experience one or more falls each year [12–15]. In fact, in a small prospective study, we have shown that functional measures such as gait speed may better predict those individuals at higher risk of fractures when compared radiological evaluation [16]. Furthermore, intervention strategies, such as exercise or rehabililation programs, are known to be effective in dialysis [17–20].

Routine evaluation of functional status and exercise regimes have been advocated for all patients established on dialysis [21]. A variety of physical function tests are available [22] however few are used on a regular basis in dialysis units.

The objective of this study was to develop and validate a clinical tool, based on gait speed, which could be easily applied in the dialysis setting. We adapted standard gait speed tests for use with elderly dialysis patients during regular visits to the haemodialysis centre. As patients are routinely weighed before and after dialysis we anticipated that the time taken to walk the distance between the dialysis chair and the weighing scale (the Sit-to-Scale test, STS) would be similar each day; would vary with functional status and could be used to predict the acute onset of functional disability.



   Subjects and methods
Top
 Introduction
 Subjects and methods
Results
 Discussion
 References
 
Patient population
This study was performed over a 20-week period at the Geriatric Dialysis Rehabilitation Program, Toronto Canada [20]. In brief this program is a collaborative program involving two University of Toronto affiliated academic institutions; the Toronto Rehabilitation Institute (TRI) and the University Health Network (UHN). The program includes a purpose-built 6-station dialysis suite housed on the ground floor of the TRI and beds on the geriatric rehabilitation ward. The ward unit offers inpatient geriatric rehabilitation services to haemodialysis-dependent seniors who have a history of acute functional decline. Patients undergo 2 h of short daily dialysis in this facility. As the population admitted to this dialysis program include a large number of frail dialysis patients from across Toronto [20], they were felt to be a suitable study population. Previous reports have shown that >70% of patients admitted to this program have demonstrable improvements in functional status allowing STS responsiveness scores to be evaluated.

Ethical approval was obtained from the Research Ethics Board of the University Health Network and Toronto Rehabilitation Institutes.

Study design
The reliability, validity and practicality of the ‘Sit-to-Scale’ Test (STS) was measured using a longitudinal prospective study design. Dialysis patients who underwent inpatient rehabilitation treatment after a decline in functional status were recruited to allow assessment of the responsiveness of the test.

Inclusion and exclusion criteria
Inclusion criteria included all patients admitted to the Geriatric Dialysis Rehabilitation Program regardless of initial ambulatory status. Exclusion criteria were limited to those patients that were unable to provide informed consent. The ‘Sit-To-Scale’ Test was performed from the time that patients were able to first walk without the supervision or physical assistance from a physiotherapist. Patients were permitted to use their regular walking aids to walk.

Measurements
Baseline demographics and clinical characteristics (age, sex, dialysis vintage, primary renal disease, medical reason for rehabilitation, Charlson Index score [23]) of the study population were obtained from the clinical database used for electronic charting. The individuals involved in the prospective data entry for the clinical database were not involved in the study protocol.

Patients were seen and asked to perform the STS at each dialysis session. Patients were asked to stand at the starting point (marked by a small sticker on the floor), and to start walking towards their dialysis chair at the count of three. Patients were reminded to walk at their normal pace (also referred to as ‘comfortable’ or ‘self-selected’ pace) and to use a walking aid if appropriate. The research assistant walked close to the patient but did not provide physical assistance. The timer was stopped when the patient crossed the 20-foot mark (similarly marked with a small sticker). Gait speed was measured to the nearest hundredth of a second using a handheld stopwatch.

Measurements were taken daily before, and after, each dialysis treatment. Walking aids, the time of dialysis treatment, and reasons for patients not being able to walk on a given day were noted. One research assistant administered the test, recorded all measurements, and documented problems with respect to the practicality of the test. Physiotherapy was consulted with once a week in order to ensure patients could safely perform the test. Ten observations were repeated by a second research assistant who had been trained in administration of the test.

Clinical functional change was objectively measured using the Functional Independence Measure [24] (FIM) score. In keeping with National Reporting Standards in Canada for all rehabilitation facilities, the severity of functional impairment, as measured by the FIM score, was prospectively recorded at the time of admission and on discharge. Two individuals assumed responsibility for scoring. Consisting of 13 motor and 5 cognitive domains, the FIM instrument is a widely used rehabilitation outcome measure, and has well-established validity and reliability for this use [24–28]. Each domain is graded on a 7-point ordinal scale with a maximum summative score of 126 (corresponding to optimum independence). The rehabilitation team also subjectively rated the patients’ functional change over the rehabilitation period. Rankings were grouped as ‘full improvement’, ‘partial improvement’ or ‘little or no improvement’. Individuals performing the clinical scoring were blinded to the STS scores.

Statistical analysis
Patient baseline demographic and clinical characteristics, as well as reasons for missed ‘Sit-to-Scale’ Tests, were analysed using descriptive statistics. Baseline STS scores were defined as the mean of the four measures taken immediately after admission to the program. Final STS scores were defined as the mean of the four measures immediately prior to discharge.

A paired t-test was used to determine if there was a difference between ‘Sit-to-Scale’ tests performed before and after dialysis.

Test–retest reliability was tested using the final four STS scores taken prior to discharge home from the rehabilitation unit (this was arbitrarily chosen prehoc to represent the time when a patient would be otherwise stable). The intraclass correlation coefficient (ICC with two-way mixed model with measures of consistency) was used to compare values taken at the four study time points [29]. Inter-rater variability was tested using the intraclass correlation coefficient over 10 observations.

Test responsiveness was established by calculating a percentage change in scores taken during the first week of the therapy with those at the end of the admission. The correlation coefficient between change in STS scores and against the change in FIM scores was calculated as a measure of test responsiveness. In a secondary analysis the change in scores were also compared using a one-way ANOVA and unpaired t-tests against each of the clinical outcome data groups (full improvement, partial improvement, little or no improvement).

Feasibility was measured by attempting a STS test in all ambulatory patients at each dialysis session. Feasibility is reported as the percentage of tests scheduled and completed. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) software (version 11.0).



   Results
Top
 Introduction
 Subjects and methods
 Results
Discussion
 References
 
Consecutive patients admitted to the unit were approached. Thirty haemodialysis patients were recruited. Of these patients, six remained chair-bound for the full duration of the study and are therefore not included further in the study. Of the studied patients the mean age was 74.6 (SD ± 7.5). Seven individuals were unable to walk at the onset of their rehabilitation therapy but were subsequently included in the study (median duration between admission and time of STS measurement 10 days, range 6–68 days). Patients were followed for an average of 3.54 (SD ± 1.57) weeks. Baseline demographic and clinical characteristics of the study group are summarized in Table 1.


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  		Table 1. Baseline demographic and clinical characteristics of study group

 
A total of 413 STS measurements were taken. The ‘Sit-to-Scale’ scores taken before dialysis differed from the scores taken after dialysis, with respective means of 16.4 ± 11.4 and 17.3 ± 12.3 (P < 0.05). Pre-dialysis scores were used in all subsequent calculations. Reliability as measured using the ICC was 0.89 (95% CI = 0. 80–0.94). Inter-rater reliability was 0.99 (95% CI = 0.98–0.99). Responsiveness testing showed that the change in STS scores correlated inversely with the absolute change in FIM scores (r = – 0.875, P = 0.000). The mean score changes (in seconds) in patients who had fully met their rehab goals, partially met their rehab goals, or not met any of their rehab goals–were 27.0%, –12.2% and +0.8%, respectively (Figure 1). (Negative change STS scores are consistent with improved functional status.)


Figure 1
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  		Fig. 1. Figure showing the percentage change (±SEM) in STS score, from baseline, at the time of discharge for patients who had a complete recovery in physical function (A), those with partial recovery (B) and those with little or no improvement (C).

 
Feasibility was measured at 92.9% of all sessions. Few (n = 29/413, 7.1%) attempts to measure the STS were unsuccessful. The following reasons were given: patient was suffering from an acute medical condition (29.4%), patient was ‘not feeling well’ (17.6%), and physiotherapist directive to not walk due to active joint problems (53.9%).



   Discussion
Top
 Introduction
 Subjects and methods
 Results
 Discussion
References
 
Increasingly nephrologists are recognizing the need for functional assessment of older dialysis patients on a regular basis. Detailed assessment using currently valuable questionnaires are however impractical in a busy dialysis unit, mostly because of the time required to perform a through assessment but also because of the need for a quiet and private environment. Our data show that the Sit-to-Scale test is a feasible, quick and reliable functional measurement which can be taken, on a daily basis, in a dialysis unit. The test had high intra-rater, inter-rater reliability, was responsive and was feasible.

There are clear limitations of our data. The study was performed in patients that had chosen to participate in a rehabilitation program suggesting a high level of motivation. Nevertheless, the data clearly show that the STS is a feasible and useful test which, we believe may be applied on dialysis days. Our data suggest that measurements were lower when taken before dialysis, rather than after dialysis. While this achieved statistical significance, a 0.7 s difference is probably not of clinical significance and therefore we believe that the ‘Sit-to-Scale’ Test can be performed on patients either before or after dialysis treatment without major differences in the scores. The 20-foot distance between scale and dialysis chair is a realistic distance to have in a dialysis suite, and a practical distance for physically frail older patients to walk at a comfortable pace. In addition, testing does not require expensive or complicated equipment or prolonged staff training. Sit-to-Scale test scores correlated with the functional status of patients, and changes over a median of 3 weeks were directly related to improvements in personal independence as measured by clinicians who were blinded to the STS scores. This suggests that the STS is a good surrogate measure for changes in functional status over time.

In summary we report a simple, inexpensive method that is useful both in clinical and research settings for assessment of dialysis patients’ functional status.

Conflict of interest statement. None declared.



   Notes
 
See http://www.oxfordjournals.org/our_journals/ndtplus/



   References
Top
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 

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Received for publication: 11.12.06
Accepted in revised form: 12. 6.07


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