Sensitivity to changes in disability after stroke: A comparison of four scales useful in clinical trials

Outcomes validity and reliability of the modified Rankin scale: implications for stroke clinical trials: a literature review and synthesis

BACKGROUND AND PURPOSE

The modified Rankin scale (mRS), a clinician-reported measure of global disability, is widely applied for evaluating stroke patient outcomes and as an end point in randomized clinical trials. Extensive evidence on the validity of the mRS exists across a large but fragmented literature. As new treatments for acute ischemic stroke are submitted for agency approval, an appreciation of the mRS's attributes, specifically its relationship to other stroke evaluation scales, would be valuable for decision-makers to properly assess the impact of a new drug on treatment paradigms. The purpose of this report is to assemble and systematically assess the properties of the mRS to provide decision-makers with pertinent evaluative information.

METHODS

A Medline search was conducted to identify reports in the peer-reviewed medical literature (1957-2006) that provide information on the structure, validation, scoring, and psychometric properties of the mRS and its use in clinical trials. The selection of articles was based on defined criteria that included relevance, study design and use of appropriate statistical methods.

RESULTS

Of 224 articles identified by the literature search, 50 were selected for detailed assessment. Inter-rater reliability with the mRS is moderate and improves with structured interviews (kappa 0.56 versus 0.78); strong test-re-test reliability (kappa=0.81 to 0.95) has been reported. Numerous studies demonstrate the construct validity of the mRS by its relationships to physiological indicators such as stroke type, lesion size, perfusion and neurological impairment. Convergent validity between the mRS and other disability scales is well documented. Patient comorbidities and socioeconomic factors should be considered in properly applying and interpreting the mRS. Recent analyses suggest that randomized clinical trials of acute stroke treatments may require a smaller sample size if the mRS is used as a primary end point rather than the Barthel Index.

CONCLUSIONS

Multiple types of evidence attest to the validity and reliability of the mRS. The reported data support the view that the mRS is a valuable instrument for assessing the impact of new stroke treatments.

Measurement of Upper-Extremity Function Early After Stroke: Properties of the Action Research Arm Test

OBJECTIVE

To examine the responsiveness and validity of the Action Research Arm Test (ARAT) in a population of subjects with mild-to-moderate hemiparesis within the first few months after stroke.

DESIGN

Data were collected as part of the Very Early Constraint-Induced Therapy for Recovery from Stroke trial, an acute, single-blind randomized controlled trial of constraint-induced movement therapy. Subjects were studied at baseline (day 0), after treatment (day 14), and after 90 days (day 90) poststroke.

SETTING

Inpatient rehabilitation hospital; follow-up 3 months poststroke.

PARTICIPANTS

Fifty hemiparetic subjects.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

At each time point, subjects were tested on: (1) the ARAT, (2) clinical measures of sensorimotor impairments, (3) in the kinematics laboratory where they performed reach and grasp movements, and (4) clinical measures of disability. Blinded raters performed all evaluations. Analyses at each time point included calculating effect size as indicators of responsiveness, and correlation and regression analyses to examine relationships between ARAT scores and other measures.

RESULTS

The ARAT is responsive to change, with effect sizes greater than 1.0 and responsiveness ratios of 7.0 at 3 months poststroke. ARAT scores were related to sensorimotor impairment measures, 3-dimensional kinematic measures of movement performance, and disability measures at all 3 time points.

CONCLUSIONS

The ARAT is a responsive and valid measure of upper-extremity functional limitation and therefore may be an appropriate measure for use in acute upper-extremity rehabilitation trials.

On the Analysis and Interpretation of Outcome Measures in Stroke Clinical Trials

BACKGROUND AND PURPOSE

A variety of primary end points have been used in acute stroke trials. We focus on the modified Rankin Scale, a reliable and valid ordinal outcome measure that assesses disability on a 7-point scale.

METHODS

We provide an abbreviated discussion of analytical methods for ordinal scales, and related effect size measures; we illustrate these methods and their interpretation with outcome data from the SAINT I study of NXY-059 in acute ischemic stroke.

RESULTS

The nonparametric Mann-Whitney statistic provides a straightforward method for analysis of the modified Rankin Scale, and incorporates associated measures of effect size. These measures are directly related to the concepts of Number Needed to Treat and Number Needed to Harm.

CONCLUSIONS

Our re-examination of the outcome data from the SAINT I study provides little evidence for the purported efficacy of NXY-059. More broadly, analysis and interpretation of ordinal outcome scales based on ascribed numerical values to the steps of the scale should be done cautiously. Statistical treatment of multiple primary outcome measures in acute stroke clinical trials should be established before analysis. Lastly, conflating statistical and clinical significance should be avoided.

Effects of physical training on functional status in patients with prolonged mechanical ventilation

BACKGROUND AND PURPOSE

Patients requiring prolonged mechanical ventilation (PMV) are frequently deconditioned because of respiratory failure precipitated by the underlying disease, the adverse effects of medications, and a period of prolonged immobilization. The effects of 6 weeks of physical training on the strength of respiratory and limb muscles, on ventilator-free time, and on functional status in patients requiring PMV were examined.

SUBJECTS

Thirty-nine patients with PMV were initially enrolled in the study and were assigned to either a treatment group (n=20) or a control group (n=19). Three subjects in the treatment group and 4 subjects in the control group died during the 6-week intervention period and thus their data were excluded from the final analysis.

METHODS

Subjects in the treatment group received physical training 5 days a week for 6 weeks. Strength of respiratory and limb muscles, ventilator-free time, and functional status, which was measured by the Barthel Index of Activities of Daily Living (BI) and Functional Independence Measure (FIM), were examined at baseline and at the third and sixth weeks of the study period.

RESULTS

Respiratory and limb muscle strength improved significantly at the third and sixth weeks in the treatment group compared with baseline measurements. Total BI and FIM scores increased significantly in the treatment group and remained unchanged in the control group. Effect sizes of the BI and FIM scores were 2.02 and 1.93, respectively, at the sixth week.

DISCUSSION AND CONCLUSION

The results show that a 6-week physical training program may improve limb muscle strength and ventilator-free time and thus improve functional outcomes in patients requiring PMV.

Clinical interpretation and use of stroke scales

No single outcome measure can describe or predict all dimensions of recovery and disability after acute stroke. Several scales have proven reliability and validity in stroke trials, including the National Institutes of Health stroke scale (NIHSS), the modified Rankin scale (mRS), the Barthel index (BI), the Glasgow outcome scale (GOS), and the stroke impact scale (SIS). Several scales have been combined in stroke trials to derive a global statistic to better define the effect of acute interventions, although this composite statistic is not clinically tenable. In practice, the NIHSS is useful for early prognostication and serial assessment, whereas the BI is useful for planning rehabilitative strategies. The mRS and GOS provide summary measures of outcome and might be most relevant to clinicians and patients considering early intervention. The SIS was designed to measure the patient's perspective on the effect of stroke. Familiarity with these scales could improve clinicians' interpretation of stroke research and their clinical decision-making.

Does Age Predict Outcome in Stroke Rehabilitation? A Study of 878 Chinese Subjects

BACKGROUND

The predicting value of age on stroke rehabilitation has been controversial. There is a lack of large-scale studies in the Chinese population to examine the effect of age on stroke rehabilitation outcomes. This study examines the predictors of a good outcome after rehabilitation in Chinese stroke patients with special attention to age as a factor.

PATIENTS AND METHODS

This retrospective cohort study includes stroke patients receiving a standard inpatient multidisciplinary rehabilitation program in a neuro-rehabilitation ward of a convalescence hospital in Hong Kong from January 2000 to December 2003. Functional independence measure (FIM) >or=90 was used to define a good outcome. Multivariate regression analysis was used to assess the independent predictors of a good outcome.

RESULTS

There were important differences in clinical characteristics and complications of stroke among patients of three age groups: <65, >or=65 and <80, and >or=80 years. The total FIM scores both upon admission and at discharge were lower in the older age groups. No significant difference was observed in the changes in FIM scores across these age groups. Age was not an independent predictor for a good outcome. FIM upon admission was an independent predictor for a good outcome (discharge FIM >or=90) in all patients and in individual age groups. Having employment before stroke was a predictor for good outcome in all patients. Living at home prior to stroke was a predictor for the total population and the >or=65 and <80 years group. The length of stay predicted a good outcome in the group >or=80 years.

CONCLUSIONS

Admission functional status, employment and living at home before stroke but not age per se are predictors of a good outcome following stroke rehabilitation. As older patients show comparable improvement during rehabilitation, intensive rehabilitation should not be withheld in stroke patients simply because of advanced age.

Critical Appraisal and Review of the Rankin Scale and Its Derivatives

BACKGROUND AND PURPOSE

Efforts to reduce stroke burden require accurate assessment of outcomes in order to compare treatments. The Rankin Scale and its derivatives, the Modified Rankin Scale and the Oxford Handicap Scale, taken together, are among the most common outcome measures that have been used in stroke research. The aim of this study was to perform a critical appraisal of the clinimetric properties of these scales. It was also planned to review the use of these scales in a selection of articles to illustrate concerns raised by the critical appraisal.

SUMMARY OF REVIEW

A literature search was performed using electronic databases to locate relevant articles about the reviewed scales. The scales were appraised using a structured format regarding the following properties: purpose, development, presentation, language, method of administration, content validity, face validity, feasibility, construct validity, reliability, responsiveness, and generalizability. There are concerns in each of the appraised areas regarding the clinimetric properties of these scales.

CONCLUSION

Further work is needed to improve the clinimetric properties of the reviewed scales to ensure that they are more useful tools in determining the outcome of stroke. Alternatively, a newer global outcome scale with improved clinimetric properties may be a better option for future stroke research.