Background
Cerebrovascular accident (CVA) or stroke is the fourth leading cause of death in the United States and the primary condition for admission for in-patient re-habilitation. Cerebrovascular accidents or strokes are also the leading cause of adult disability in the United States.1 The Stroke Association, located in Dallas, Texas, estimates that 795,000 Americans suffer from a stroke each year - 610,000 are new strokes, while 185,000 occur in individuals who have had a previous stroke.2 According to the World Health Organization and the World Stroke Organization, approximately 15 million individuals suffer a stroke each year worldwide.3
According to the Centers for Disease Control and Prevention, 87 per cent of CVAs are ischemic strokes, with the remaining 13 per cent being hemorrhagic.2 An ischemic stroke is defined as an interruption of blood flow in the brain due to a clot, while a hemorrhagic stroke may be characterized by a ruptured blood vessel in the brain that causes an interruption in blood flow.4 In both types of CVAs, clinical manifestations are the result of the location of the stroke and the length of time blood flow has been interrupted.4
Due to the many variables involved, post-CVA clinical manifestations and the extent of recovery vary widely among individuals. According to Anemaet,1 there are many factors that influence the degree to which an individual will recover and the level of functional independence that will be achieved following a CVA. Early identification of the stroke patient's recovery prognosis and potential for functional independence is valuable, as it allows caregivers, rehabilitation staff, rehabilitation facilities and long-term nursing facilities to identify equipment and financial resources that are required to produce the best possible outcomes for individual patients.5 Therefore, once recovery prognosis has been determined for the individual who has suffered a stroke, the next important step is to determine their potential level of functional independence. Functional independence is defined as the ability to perform the activities of daily living (ADLs) such as feeding, grooming, bathing, dressing, bowel and bladder care, toilet use and mobility.6
Multiple scales are available to measure the initial neurological deficits an individual develops immediately following a CVA and can provide some insight into recovery prognosis and the potential level of functional independence. Two of the most common scales, the National Institutes of Health Stroke Scale (NIHSS) and the Canadian Neurological Scale (CNS), are commonly used to assess stroke severity and predict recovery outcomes.7 The NIHSS allows a provider to assess an individual patient in a systematic manner and provides a quantitative measure of related neurological deficits. Lyden and Lau8 describe the NIHSS as a 15-item assessment where each item is scored on a three (3)- to four (4)-point scale, with the higher scores indicating greater deficit. "The subscale items of the NIHSS encompass level of consciousness, vision, facial palsy, limb strength, ataxia, sensation and speech and language."8(p.1348) In Demchuk et al.'s study, the higher the initial score was, the worse were the odds of a good outcome.1(p.52) Patients with an initial score of 7 or lower were 1.9 times more likely to be functionally normal, while a score greater than 20 on the NIHSS is predictive of difficulty or inability to perform basic ADLs.1
The CNS was introduced in 1986 and was developed based on a literature review and clinical experience.8 The purpose of the scale is to measure neurological deficits in post-CVA patients.1 The CNS was developed for use by neurologists and other healthcare providers providing care to patients in an acute care facility.8 The CNS comprises a scale consisting of eight items: (1) level of consciousness, (2) orientation, (3) speech, (4) motor function, (5) facial weakness, (6) face response, (7) arm response and (8) motor response.8 The scale allows the normal patient to receive a maximum of 10 points in the area of level of consciousness, orientation, speech, motor function and facial weakness. Patients who have comprehension deficits are scored in a separate section based on face, arm and motor response. In contrast to the NIHSS, where a higher score indicates greater deficits, a lower score in the CNS indicates greater severity.9 The CNS is also used to predict recovery prognosis and functional independence. Patients with a low total score have lower functional independence.8
In summary, a CVA is often a devastating event for patients and their families. The cost of initial treatment and rehabilitation is expensive, and some individuals never regain functional independence following a stroke. Healthcare providers, patients, families and third parties will likely find it helpful to have the most accurate assessment of an individual's stroke severity, recovery prognosis and potential for functional independence following a CVA to make an informed decision about how resources should be expended for treatment and rehabilitation. Scales to measure post-CVA neurologic status and predict recovery outcomes may provide useful tools for gauging and guiding treatment needs.7 However, for effective and optimal use of scale results, the scales must be psychometrically sound. There has been at least one systematic review published that evaluated the ability of functional independence measures (FIM) to predict functional outcomes of a stroke-specific population.10 In this review, the FIM was used to evaluate the functional status of patients throughout rehabilitation.10 Salbach et al.11 considered CNS scores in determining responsiveness and predictability of gait speed and other disability measures in acute strokes. To date, the Cochrane Database of Systematic Reviews, the JBI Database of Systematic Reviews and Implementation Reports, PROSPERO, PubMed and CINAHL were searched and no published systematic reviews were found detailing the psychometric properties of commonly used measures of neurologic status used in predicting recovery prognosis and functional independence. Based on this information and to help fill this current evidence gap, a systematic review will be completed to answer the question, "Are the measures of neurologic status that are used in adults who have had a CVA valid in predicting functional independence?" This systematic review will focus specifically on the psychometric properties of the NIHSS and CNS.
Inclusion criteria
Types of participants
Participants will be adults, 18 years and older, with a confirmed medical diagnosis of a CVA. Cerebrovascular accident will be defined as a sudden loss of neurological function, caused by vascular injury to an area of the brain.5
Types of measures
The current review will consider studies that evaluate the use of the NIHSS and the CNS for assessing neurological status to predict functional independence in adults who have suffered a CVA.
Outcomes
Studies that examine the predictive validity in terms of functional independence of the NIHSS and CNS measurement tools will be included in this review.
Types of studies
The current review will consider studies that are observational and cross-sectional in nature.
Search strategy
The search strategy aims to find both published and unpublished studies. A three-step search strategy will be utilized in this review. An initial limited search of PubMed and CINAHL will be undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe the article. A second search using all identified keywords and index terms will then be undertaken across all included databases. Third, the reference list of all identified reports and articles will be searched for additional studies. Studies published in English will be considered for inclusion in this review. Studies published since 1991 will be considered for inclusion in this review. These dates were chosen because in 1991 Lyden and Lau8 completed a critical appraisal of stroke evaluation and rating scales. It was in this review that the NIHSS and CNS were determined to have some predictability of patient outcomes.
The databases to be searched include: CINAHL, PubMed, PsycINFO and Embase.
The search for unpublished studies will include: ProQuest Dissertations and Theses Mednar.
Initial keywords to be used will be: stroke; cerebral infarction; cerebral accident; stroke scale; stroke assessment; NIH Stroke Scale; Canadian Neurological Scale; ischemic; cerebrovascular; functional independence; Barthel Index; Functional Independence Measure; Functional Assessment Measure; iScore; predictive validity.
Assessment of methodological quality
Assessment of the methodological quality will be undertaken through the COSMIN checklist.14 The COSMIN checklist is a 4-point scoring system used to evaluate the methodological quality of studies examining the measurement properties of an instrument; specifically for systematic reviews.12 Papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review. Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.
Data extraction
Data will be extracted from papers included in the review using the COSMIN data extraction tool.14 Two independent reviewers will extract data. The data extracted will include specific details about the study quality, study methods and objectives, and outcomes significant to the review question and objectives. Any disagreement that arises between the reviewers will be resolved through discussion or with a third reviewer. The authors of primary studies will be contacted where necessary for clarification or missing information.
Data synthesis
Effect size associated with internal consistency and inter-rater reliability (such as Cronbach's alpha, Cohen's kappa inter-rater scores and/or Kendall's tau) will be reported. If statistical pooling is not possible, the findings will be presented in a narrative form including tables and figures to aid in data presentation where appropriate.
Acknowledgements
We would like to acknowledge University of Mississippi School of Nursing for support of the project.
References