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Research Reports |
NC Landgraff, PT, PhD, is Associate Professor, Department of Physical Therapy, Youngstown State University, Youngstown, Ohio
SL Whitney, PT, PhD, NCS, ATC, is Associate Professor, Department of Physical Therapy, University of Pittsburgh, Pittsburgh, Pa
EN Rubinstein, PhD, is Adjunct Assistant Professor, Department of Health Information Management, University of Pittsburgh
H Yonas, MD, is Chairman, Department of Neurosurgery, University of New Mexico, Albuquerque, NM
(nlandgraff{at}ysu.edu) Address all correspondence to Dr Landgraff at 7121 Ronloy Pl, Boardman, OH 44512 (USA)
Submitted March 16, 2005;
Accepted October 19, 2005
 | Abstract |
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=27 of 36; 7-item PPT, =21 of 28). Subjects with moderate stenosis were the slowest in performing the task of simulated eating. Discussion and Conclusion. Subjects with asymptomatic carotid artery stenosis and occlusion exhibited changes in function, as indicated by their performance on the PPT relative to that of a comparison group. This finding may be indicative of preclinical disability, indicating that these people are symptomatic. This indication may affect the medical and surgical options that can be considered for their care. [Landgraff NC, Whitney SL, Rubinstein EN, Yonas H. Use of the Physical Performance Test to assess preclinical disability in subjects with asymptomatic carotid artery disease. Phys Ther. 2006;86:541–548.]
Key Words: Activities of daily living • Cerebrovascular disorders • Geriatric assessment • Predictive value of tests
| Introduction |
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It is has been found through clinical observations and the use of performance-based measures that subjects demonstrate impaired physical function but do not self-report any difficulty with a task.2,4 In a long-term study of the physical activity and functional status of community-dwelling older women, Brach et al4 found that the use of the Physical Performance Test (PPT), a performance-based measure, identified more limitations in physical function than did self-report functional questionnaires. The researchers reported that the use of a performance-based measure increases the likelihood of identifying slight declines in physical function.4
The PPT is a direct observational test that assesses multiple dimensions of physical function (basic and complex activities of daily living [ADL]) with different levels of difficulty.5 The principal target population for the PPT was older adults, and the original study tested subjects from 49 to 94 years of age, with an average age of 79 years.5 These subjects were from a variety of populations: patients at outpatient geriatric practices, residents of a senior citizen housing unit, patients in a hospital primary medical care unit, and people entering a board-and-care home. The developers of the PPT suggested that it could be useful in the prediction of functional decline in subjects.5
The PPT is a compilation of items mimicking basic and complex ADL tasks and is scored by timing the completion of a task. This time then is related to a categorical score of 0 to 4, in which 4 represents people in the fastest 20% at completing the task, 1 represents those in the slowest 20%, and 0 represents those who cannot complete the task. The maximum score on the 9-item PPT is 36, and the maximum score on the 7-item PPT is 28.5 Reuben and Siu5 reported a 9-item PPT mean score of 26.8 for a senior citizen housing group. Mean 9-item PPT scores for geriatric practice and medical clinic groups were 22 and 24.7, respectively.5 For their sample of 106 subjects, the range on the 9-item PPT was 2 to 35.5
The PPT has been shown to demonstrate internal consistency (Cronbach alpha=.87) and interrater reliability (r=.99).5 It also has been shown to demonstrate concurrent validity with other functional performance measures, such as the Katz ADL scale.6 In that study, the PPT was the test of choice to use as a predictor of physical decline because of its strong psychometric properties and ease of completion in a clinic.
Health care professionals who care for patients with reported asymptomatic carotid artery disease suspect that some patients may not be functioning as well as they report. These patients have the disease process of atherosclerotic plaque buildup inside the carotid artery wall to various degrees. People with 50% to 69% blockage of the carotid artery are considered to have moderate disease, those with 70% to 99% blockage are considered to have severe disease, and those with complete blockage are considered to have occlusion.7,8 The risk of stroke is different for each of these subgroups and is considered negligible until the artery demonstrates at least 90% blockage.9–11 Asymptomatic carotid artery disease typically is identified as an incidental finding during a medical workup for an unrelated purpose.
It has been found that changes in physical, cognitive, and emotional function escape being communicated in the clinical history and examination of people with asymptomatic carotid artery disease.12 As these people undergo further evaluation, they tend to report no clinical signs and symptoms that would indicate a problem with function related to carotid artery stenosis or occlusion. These signs and symptoms, such as numbness, tingling, or weakness on 1 side of the body, loss of vision, slurred speech, or problems finding words, would be the warning signs of a transient ischemic attack.13,14 Such symptoms would affect physical function. Stroke risk has been found to be more dramatic for people with any of these symptoms than for asymptomatic individuals.8,15–18 Thus, the medical management has been different, and surgical intervention, such as a carotid endarterectomy, which has been shown to significantly reduce the risk of stroke in symptomatic people, is not offered readily to asymptomatic people.18–21 However, if it can be determined that people with asymptomatic carotid artery disease may be displaying subtle declines in function (a characteristic of preclinical disability), then the medical and surgical management of these people may change in order to affect the incidence of stroke through early prevention and intervention.
Therefore, the purpose of this study was to determine whether people with asymptomatic carotid artery stenosis and occlusion demonstrate deficits in physical performance that may indicate a state of preclinical disability. We expected to find that there was no deficit in physical performance between subjects with disease and a comparison group when assessed with the PPT. This study was part of a larger study that considered cognitive function and instrumental ADL as additional indicators of impaired function in asymptomatic people with carotid artery disease.
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Seventy-one comparison subjects were previously recruited from an aging study (National Institutes of Health, AG10009) by the second author. All subjects were examined by a board-certified neurologist and had normal vision plus normal age-adjusted hearing. Sensation, as tested with Semmes-Weinstein monofilaments, was normal, and the Mini-Mental State Examination scores were all greater than 24, indicating no cognitive impairment.22 Comorbidity data were not recorded for the comparison group; however, the subjects were all living independently in the community and were considered healthy and functional by the investigators. All of the comparison group participants could ambulate up and down 4 flights of stairs without complaint.
Measures
The 9-item PPT and the 7-item PPT were used to assess physical function, and the 7 timed tasks on the test were analyzed individually.5 The PPT is a global measure of physical performance that assesses performance of basic and complex ADL tasks.5 The 9-item test includes the following items: writing a sentence, simulated eating, donning and doffing a jacket, turning 360 degrees right and left, lifting a book to a shelf, picking up a penny from the floor, walking 15 m (50 ft), climbing 1 flight of stairs, and climbing several flights of stairs (a maximum of 4). In the 7-item test, the tasks of climbing 1 flight of stairs and several flights of stairs were eliminated from the scoring. On the 9-item PPT, a score of 36 is the highest score possible, and on the 7-item PPT, a score of 28 is the highest score possible; these highest scores would be considered to indicate optimal performance.
The PPT was used in this study to determine whether any unreported motor, sensory, or cognitive problems were affecting a subject’s physical function. Test items were timed with a standard stopwatch, and times were rounded off to the nearest 10th of a second. The time for task completion was recorded. Time also was converted into an ordinal scale (0–4) as suggested for the original test.5 The PPT was administered only by the primary investigator for the study, who was aware of the carotid artery disease state of the subject. The test was administered and scored according to the protocol published by Reuben and Siu.5 The primary investigator has performed interrater reliability testing for the PPT with a coauthor who has tested a few hundred subjects and has published articles regarding the use of the test. Strong interrater reliability was found (r=.92).
Data Analysis
Descriptive statistics were computed for the demographic data for the subjects, including medications, comorbidities, and scores on the 9-item PPT and the 7-item PPT. An analysis of variance (ANOVA) was used to determine whether there were significant differences among the 6 subject groups with regard to severity of disease, unilateral versus bilateral involvement, and laterality of the disease. Descriptive statistics also were computed for the 9-item PPT and 7-item PPT scores for the comparison group. Independent t tests were used to determine whether there were differences between the comparison group and the carotid artery disease group on the 7-item PPT and the 9-item PPT. Pearson correlation coefficients were calculated for the PPT scores and the number of comorbidities that a subject had as well as the number of medications that a subject reported taking.
Mean 9-item PPT and 7-item PPT scores were calculated and compared with the maximum scores of 36 and 28, respectively. A lower score indicates that a subject needs more time to complete a task on the PPT, thus suggesting the beginning of physical decline and possibly preclinical disability.1,4
| Results |
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The most common comorbidities that the asymptomatic subjects had were hypertension (39%), hypercholesteremia (36%), diabetes mellitus (33%), coronary artery disease (31%), and cardiac arrhythmia (13%). Additionally, there were some comorbidities that did not relate to carotid artery disease, such as nondisabling cancers, cataracts, diverticulitis, and arthritis. Minor arthritis was present in 8.3% of the asymptomatic subjects. Disabling arthritis that would impair performance on the PPT was an exclusion criterion for the study. No single comorbidity was present in a majority (50% or greater) of the asymptomatic subjects. The highest incidence was for hypertension, which was present in 39% of the asymptomatic subjects. Within the asymptomatic group, 46.1% of the subjects had 3 or more of the comorbidities described, and 53.9% had 2 or fewer comorbidities. Pearson correlation coefficients indicated that there was no significant relationship between the number of comorbidities in the subjects and their performance on the PPT (r=.07). Comorbidity data were not collected for the comparison group.
A wide variety of medications were being taken by the subjects with carotid artery disease. The most common categories of medications were central nervous system agents, which included 5 different medications, antihypertensives, and antilipemics. The 2 most common medications were aspirin (54%) and the antilipemic simvastatin (Zocor*). Again, no significant relationship was found between the number of medications that the subjects were taking and their performance on the PPT (r=–.14). No medication data were available for the comparison group.
Physical performance was analyzed from 2 perspectives: the severity of carotid artery disease and the laterality of disease. In order to determine differences in performance among severity groups, an ANOVA was completed. No significant difference was found among the groups (unilateral or bilateral moderate or severe disease or occlusion) on any of the physical performance measures at a level of significance of P<.05.
For the 9-item PPT, we found that no subject achieved a maximum score of 36. Scores ranged from 14 to 34, with mean scores of 27 of 36, for all asymptomatic subjects; for control subjects, the range was 22 to 35, with a mean score of 30 of 36 (Tab. 2). No subject achieved a maximum score of 28 on the 7-item PPT. The range of scores for the carotid artery disease group was 14 to 27, with a mean score of 21 of 28. The range of scores for the comparison group was 20 to 25, with a mean score of 23 of 28 (Tab. 3). Independent t tests for group differences revealed significant differences between the comparison group and subjects with carotid artery disease on both the 7-item PPT (P<.03) and the 9-item PPT (P<.00).
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The PPT individual tasks also were timed and recorded. A detailed analysis of each of the timed items was conducted. Table 4 shows a summary of the items for which time was recorded for the asymptomatic subjects. Further analysis was performed to determine whether there were differences on any PPT timed item on the basis of the severity of carotid artery disease for the unilateral and bilateral moderate stenosis, unilateral and bilateral severe stenosis, and unilateral and bilateral occlusion subgroups. Mean scores, standard deviations, and ranges for the PPT timed items are shown in Table 5. An ANOVA was performed to determine whether there were differences in time to complete the tasks for these 3 subgroups (Tab. 6).
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| Discussion |
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Subjects with moderate and severe stenosis and occlusion performed below the maximum score on the 9-item PPT and the 7-item PPT. Additionally, those with moderate stenosis (50%–69%) performed the worst, with an average 9-item PPT score of 24 of 36 and a 7-item score of 19 of 28. These mean scores were related to the percentile rankings established for adults 65 years of age and older (from the study describing the original test) on the 9-item PPT, as the average age of participants in this study was 73 years and the mean age of the participants in the other study was 79 years.5 The average score for subjects with moderate stenosis placed them at approximately the 50th percentile of physical function, the average score for subjects with severe stenosis (28 of 36) placed them just below the 75th percentile of physical function, and the average score for subjects with occlusion (26 of 36) placed them at approximately the 60th percentile of physical function.5 On the 7-item test, the percentiles were approximately the same, with the exception that the average score for subjects with occlusion placed them at the 75th percentile of physical function, instead of the 60th percentile on the 9-item test.5 In this study, the results indicated that at all levels of carotid artery stenosis and occlusion tested, the subjects demonstrated less than optimal performance. In a study evaluating physical decline in community-dwelling older women, Brach et al4 defined clinical decline as a score below 4 (the highest score) on a PPT item. Fried et al1 indicated that a score lower than the maximum score would be significant for preclinical disability.
In this study, 100% of the asymptomatic subjects with carotid artery stenosis and occlusion demonstrated scores at least 25% below optimal function, yet only 19% of the comparison group had scores 25% below optimal function. Thus, it is suggested that all of the asymptomatic subjects tested demonstrated a functional decline that might be associated with early clinical symptoms of carotid artery disease.
When the PPT scores were analyzed from the perspective of laterality of disease, the results also suggested preclinical disability, with a mean score of 28 of 36 (75th percentile) when either the right side or the left side was the affected artery and a mean score of 26 of 36 (60th percentile) when both sides were involved. It was interesting to note that bilateral involvement led to a more impaired status. This is a reasonable finding, as impaired blood flow to both sides of the brain should affect function more profoundly.
The PPT items were chosen to indicate different levels of difficulty across the items and to reflect different dimensions of function, specifically upper fine motor function, upper "coarse" motor function, balance, coordination, mobility, and endurance.5 In order to analyze the physical function of the subjects in this study in more detail, an analysis of time to perform each task was done to determine whether any task was significantly more difficult (took more time to complete) for any group of subjects.
When the 3 subgroups of subjects were compared, the subjects with moderate stenosis demonstrated a significant difference in time to complete simulated eating. This item has been identified as demonstrating a perceived minimal level of difficulty.5 Each item also reflects a different functional dimension that the test was developed to assess. For example, simulated eating was designed to test upper fine motor function.24 An explanation for the deficit on this task might be related to the patterns of blood flow and loss of blood flow to the brain, as internal carotid artery stenosis might compromise flow to the areas of the brain responsible for the function of simulated eating. The physiology of blood flow to the brain and compromise thereof remain areas of continued study.25–27 In cases of carotid artery occlusion, there is an increase in collateral blood supply from the opposite side of the brain that compensates for the lack of flow to the side of the brain fed by the occluded carotid artery.28 Additionally, Derdeyn et al29 found that asymptomatic subjects with carotid artery occlusion were at a much lower risk of demonstrating an impaired hemodynamic state than were subjects with symptoms. However, this parameter has been researched only for carotid artery occlusion. The data from this study demonstrated a functional decline in all asymptomatic subjects and a significant difference for a particular task in subjects with moderate stenosis. No studies have addressed the hemodynamic state of people with stenosis. The detection of impaired functional performance leads us to consider that these individuals may not be truly asymptomatic and may demonstrate some degree of preclinical disability.1 Further research is needed to assess both the physiologic status of blood flow in people with carotid artery disease and the functional status to determine whether signs of disability are being overlooked in the clinical assessment of these people.
The relatively small total sample size (n=39) and the unequal numbers of subjects within subgroups based on severity of disease are limitations of this study. Another limitation was the use of a single rater who was aware of the subjects’ diagnostic status. Finally, the presence of other comorbidities in subjects with carotid artery disease may have contributed to the compromised performance on the PPT, so that this performance may not be related solely to the carotid artery disease. However, despite these limitations, we believe that the results are impressive enough to substantiate the argument that people who are asymptomatic may not be functioning optimally. Substandard performance on the PPT may be considered a "symptom" for these people, possibly increasing their risk for stroke. Monitoring these asymptomatic people over time may help to suggest whether the PPT can help to predict the incidence of stroke or transient ischemic attack. Additionally, assessing physical performance (in people who require intervention) before and after carotid endarterectomy would help to establish whether this subtle functional decline can be affected positively by an intervention.
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| Footnotes |
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This study was approved by the Institutional Review Board of the University of Pittsburgh Medical Center.
A portion of this study was supported by the National Institutes of Health (AG10009 and AG14116).
* Merck & Co Inc, PO Box 4 WP39–206, West Point, PA 19486–0004. 
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