Trunk Control Test as an Early Predictor of Stroke Rehabilitation Outcome

Subjects and Methods

Results

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 r_s=.41 (P=.004) to r_s=.83 (P=.0001), with the exception of T3 and T4 at discharge (r_s=.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 (r_s=.831 for the TCT, r_s=.857 for the FIM, r_s=.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.

Discussion

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 patients^{2 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