Background and Purpose The aim of this study was to investigate the construct and predictive validity of the Trunk Control Test (TCT) in postacute stroke patients by comparing TCT scores at admission and discharge with the Functional Independence Measure (FIM) scores.
Methods Forty-nine patients participated in the study. The TCT examines four movements: rolling from a supine position to the weak side (T1) and to the strong side (T2), sitting up from a lying-down position (T3), and sitting balance (T4). The FIM is an 18-item scale (13 motor [motFIM] and 5 cognitive [cognFIM]) used to determine the level of dependence of patients in daily life.
Results Thirty-six patients (73%) increased their TCT overall score at discharge. The TCT item-total correlations were high, both at admission and discharge (P<.0001). The individual TCT items were intercorrelated. Furthermore, the homogeneity of the TCT was confirmed by a high Cronbach’s index. High correlations were found between admission and discharge scores in the different tests (TCT, FIM, and motFIM; P<.0001) and between TCT at admission and FIM (P<.0001) and motFIM (P<.0001) at admission. TCT at admission alone explained 71% of the variance in motFIM at discharge.
Conclusions The TCT showed a good sensitivity to change in assessing recovery of stroke patients. The high item-total correlation and Cronbach’s α value of the TCT suggest that there is one homogeneous construct underlying the item list. The TCT construct validity was confirmed by the correlation between this test and the FIM scores. TCT at admission predicted motFIM at discharge even better than motFIM at admission alone. Possibly, the TCT captures basic motor skills that foreshadow the recovery of more complex behavioral skills described by the FIM.
In patients with recent hemiparesis, trunk movement control is an indispensable basic motor ability for the execution of many functional tasks.1 The value of an early assessment of sitting balance in predicting the functional outcome of stroke patients has been pointed out in recent studies.2 3 4 However, the data from these three studies deal only with the capacity to maintain the sitting position in static conditions or at most in resistance to a nudging maneuver, a postural task which most patients are able to carry out quite early after stroke.3
Recently, a new test has been proposed for the evaluation of trunk control in stroke patients, ie, the TCT, which, besides the maintenance of the sitting position, also examines the ability to roll from a supine position towards the “weak” and “strong” sides as well as the transfer from supine to sitting position.5 The pilot study has demonstrated both the reliability of the TCT and its capacity at 6 weeks after stroke to predict the recovery of walking ability by 18 weeks. The study, however, pointed out the need for further analysis of other psychometric properties of this short simple test.5
The aim of this study was to investigate both the construct and predictive validity6 of the TCT in patients affected by recent hemiparesis admitted to a rehabilitation center by comparing the scores on this test at both admission and discharge with those on the FIM,7 a valid measure of disability widely used in patients with hemiparesis.8 9
Subjects and Methods
Forty-nine patients participated in the study. They were consecutively admitted after a first stroke from April through December 1994 at the Department of Neurology of a free-standing, 300-bed rehabilitation center. Patients were referred from surrounding acute-care hospitals.
The 49 patients (24 men, 25 women) had a mean±SD age of 68±13 years (range, 38 to 83 years). Of these patients, 12% were single, 53% married, and 35% widowed or separated. Twenty-eight patients had right hemiparesis, and 21 left hemiparesis. The cause of the stroke was thromboembolic in 40 patients (82%) and hemorrhagic in 9 (18%). Confirmation of the diagnosis was made by a neurologist according to WHO criteria10 with the aid of CT scans. No patient presented major medical comorbidities that would make assessment of motor function very difficult. The average interval from onset of stroke to admission for rehabilitation was 46 days (median, 40; range, 31 to 78), while average length of stay was 44 days (median, 43; range, 21 to 72). Patients underwent an average of 450 minutes per week (6 days per week) of physical therapy, occupational therapy, and where necessary, speech therapy.
The study was approved by the review committee of our center. All patients signed an informed consent before entering the study.
The TCT5 examines four axial movements: rolling from a supine position to the weak side (T1) and to the strong side (T2), sitting up from a lying-down position (T3), and sitting in a balanced position on the edge of the bed with feet off the ground for 30 seconds (T4). The scoring is as follows: 0, unable to perform movement without assistance; 12, able to perform movement but in an abnormal manner; and 25, able to complete movement normally. The TCT score is the sum of the scores obtained on the four tests (range, 0 to 100). The examiner’s score must relate solely to the performance during the test and not be based on referred data.
The FIM is an ordinal scale composed of 18 items with seven levels ranging from 1 (total dependence) to 7 (total independence) designed to determine the level of disability of patients, as reflected by their need for assistance and/or aids during the execution of activities of daily living.
The FIM can be subdivided into a 13-item motor subscale (motFIM) and a 5-item cognitive subscale (cognFIM).11 The ranges of scoring for the motor and cognitive subscales are 13 to 91 and 5 to 35, respectively.
The data for the two tests were collected simultaneously, within a period of 72 hours after admission (-adm) and preceding discharge (-dis).
The TCT was administered in accordance with the guidelines established in the validated Italian version13 by a single observer, a physiatrist (M.M.T.). The FIM assessment was made according to the validated Italian version13 by a single observer, a physiatrist (R.C.) trained and accredited in Italy through the Copyright Owner Agency (UDSmr, State University of New York, Buffalo, NY). The rater gathered information from observation and direct interview with the patient, integrated where necessary by data supplied by relatives, the therapist, and nursing personnel, in accordance with the standard procedures outlined in the FIM manual. The two observers were blind to each other’s records.
Median values were preferred to means when distribution of the data was skewed.
Correlation coefficients between variables were calculated using Spearman’s rank method, corrected for ties, in view of the ordinal nature of both TCT and FIM raw scores. We used the Bonferroni adjustment to correct the significance levels (P) for correlation coefficients (rs).
The internal consistency of the TCT was tested using Cronbach’s α, both at admission and discharge. The homogeneity of the TCT items was also checked by calculating the correlations of each individual item with the scale total after omitting that item.14
The significance (P<.05) of differences between initial and final scores was calculated with use of the Wilcoxon sign test. To predict the value of motFIM-dis on the basis of total and single-item values of the TCT and FIM at admission, a multiple linear-regression model was adopted, using forward stepwise regression with elimination of nonsignificant variables (Statview TMII software, Abacus Concepts Inc, 1988).
Table 1⇓ shows the median and interquartile range of TCT and FIM total scores, as well as of the subscores of motFIM, cognFIM, and the four items of the TCT at admission and discharge.
The median (range) of the scores for TCT-adm and TCT-dis were 36 (0 to 100) and 61 (0 to 100), respectively, while those for FIM-adm and FIM-dis were 59 (18 to 103) and 70 (31 to 123), respectively. The differences between scores at admission and at discharge were found to be significant for both the TCT and FIM (P<.001).
Thirty-six patients (72%) changed the overall TCT score at discharge: 20 patients showed an increase for T1, 18 for T2, 12 for T3, and 20 for T4. Minimal and maximal scores in finite scales do not allow precise estimation of subjects’ performance.
Seven of a total of 49 patients obtained the top score on the TCT at admission and 14 patients at discharge. Fifteen patients obtained the top score for T1 at admission and 25 at discharge; for T2, the numbers were 12 and 20; for T3, 9 and 15; and for T4, 20 and 44, respectively. The score for each item of the TCT showed a high correlation with the sum of the scores for the remaining three items, both at admission and discharge, with values ranging from .49 to .816 (P<.0001) (Table 2⇓).
The individual items presented significant intercorrelations, with values ranging from rs=.41 (P=.004) to rs=.83 (P=.0001), with the exception of T3 and T4 at discharge (rs=.324, P=.025).
Cronbach’s index suggests that the items of the TCT describe a homogeneous variable: the values for the TCT at admission and at discharge were α=0.86 and α=0.83, respectively.
In the different tests (TCT, FIM, and motFIM), the scores at admission were highly correlated with the corresponding scores at discharge (rs=.831 for the TCT, rs=.857 for the FIM, rs=.858 for the motFIM; for all P<.0001).
The TCT-adm correlated also with the totFIM (-adm .707, -dis .79; P<.0001 for both) and with the motFIM (-adm .819, -dis .856; P<.0001 for both), as well as with various motor items of the FIM (Table 3⇓). Both at admission and discharge, significant correlations were found with the following items: grooming, dressing upper body, toileting, sphincter control, transfer from bed/chair, toilet transfer, and walking/wheelchair locomotion.
No significant correlation was found, however, between TCT-adm and cognFIM (either individual or total scores) or between cognFIM and motFIM, either at admission or at discharge.
The predictive equation of motFIM-dis, as a function of either the cumulative or single-item scores of the TCT and of the FIM at admission, was motFIM-dis=15.145+0.272 TCT-adm+0.543 motFIM-adm (r=.881, R2=.776; P<.001). TCT-adm alone explains 71% of the variance of motFIM-dis.
About 75% of the patients showed an increase in TCT scores during their in-hospital stay. The TCT test thus showed a good sensitivity to change.
The order of increasing difficulty of the items, based on their cumulative score, was as follows: sitting balance, roll from supine to involved side, roll from supine to sound side, and sitting up from a lying-down position. This order remained unchanged at discharge, suggesting the intrinsic stability of the scale.
This hierarchy also makes clinical sense. (1) The “static” performance was easier than the three “dynamic” performances. (2) The “turning” performances, in which one can rely on compensatory motions of the unaffected limbs, were found to be easier than the “come to sit” performance, which requires muscles of both sides, as also noted by a recent study.15 (3) It is likely that the difficulty with this latter task is in part due to the impairment in abdominal strength. It has been recently pointed out that trunk muscle strength is impaired multidirectionally in stroke patients and that the impairment is greatest in forward flexion.16
Results also indicate that only maintenance of the sitting position (T4) is likely to present a ceiling effect at approximately 3 months from the stroke. In this item, 90% of the patients obtained the top score at discharge despite the fact that the sample analyzed had, with respect to the “average” American stroke patient,9 a lower independence (as measured by the FIM) after a longer time span between stroke and rehabilitation onset.17 The prognosis could thus be considered as less favorable than in the US population, given that the possibility of a spontaneous recovery of motor functions immediately after the acute episode declines progressively over the course of a few months.18 19
The correlations between each item of the TCT and the sum of the remaining items, at both admission and discharge, and the high values of Cronbach’s index suggest that there is at least one homogeneous construct underlying the item list.20 However, top and minimal scores in different items were far from exceptional in our sample. This might have artificially increased the between-item correlation so that further confirmation of the homogeneity of this test is needed, with use of other valid approaches (eg, Rasch analysis).21
The high correlations between TCT on the one hand and motFIM and total FIM on the other provide further evidence of the construct validity of TCT in severely impaired stroke patients. Of interest is the fact that at hospital admission a trunk mobility test can predict motFIM-dis even better than the motFIM-adm alone.
Possibly, TCT explores motor performances that in poststroke patients represent low levels of a unique motor competence.15 22 Trunk control appears to be an obvious prerequisite for the control of more complex limb activities that in turn constitute a prerequisite for complex behavioral skills. In other words, the recovery of more basic motor skills might precede the appearance of more refined motor behaviors.23 24 Along the same line of thought, other selected tests of strength in simple tasks, such as the hand grip25 and segmental motion of lower extremity,26 have also proved in the early poststroke stages to be predictive of recovery in more complex tasks.
Previous studies that have addressed the capacity of a trunk motor assessment to predict functional independence in stroke patients2 3 4 produced results in agreement with our own. However, they are not precisely comparable with ours for several reasons: (1) they assessed sitting balance only,2 4 (2) they rated independence at a different stage with respect to our trial,2 3 and (3) they used the Barthel Index rather than the FIM to assess independence.2 3 4
The lack of correlation of TCT scores with the cognFIM scores is explainable by the fact that often, as in our case, cognitive disability does not fully correlate with motor disability, so that an independent analysis of these two domains has been advised for FIM scores themselves.9 Moreover, the TCT probably works best around or below the “floor” of the motor FIM subscale, where elementary motor performances, though recovered, are not yet sufficient to trigger the complex motor and cognitive skills captured by the FIM items.
Selected Abbreviations and Acronyms
|FIM||=||Functional Independence Measure|
|cognFIM||=||5-item cognitive subscale of FIM|
|motFIM||=||13-item motor subscale of FIM|
|TCT||=||Trunk Control Test|
|WHO||=||World Health Organization|
This study was supported in part by Grant “Ricerca Corrente 1995” from the Ministero della Sanità, Rome, Italy.
- Received April 12, 1997.
- Accepted April 28, 1997.
- Copyright © 1997 by American Heart Association
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