1 Introduction
Stroke, affecting nearly 800,000 individuals, and approximately 15% to 30% of stroke survivors experiencing permanently disabled as a direct consequence.[1,2] [3] [4,5] [6]
A variety of ADL assessment scales had been used for stroke patients. These included the Barthel Index (BI),[7] [8] [9] [10] [11]
BI was originally established for assessing the ADL of stroke patients and has been widely used in stroke patients.[7,12] [8,13]
Rasch model is a probability mathematical model, which can evaluate whether the items have good quality in reflecting the response parameters of patients.[14] [14] [14] [15,16]
Therefore, in the current study, we applied the Rasch model to examine the reliability and validity of MBI in a disabled IS population, to assess the applicability of MBI in IS patients with limb dysfunction.
2 Methods
2.1 Sample and procedures
In this study, we retrospectively reviewed the data of consecutive patients recruited in the CIRCLE study (ClinicalTrials.gov ID: NCT03702452) between November 21, 2018 and November 19, 2019. The CIRCLE study was to verify that nursing-directed rehabilitation in IS patients can compensate for the shortage of professional rehabilitation therapists. The inclusion criteria:
(1) between 18 and 90 years old;
(2) diagnosed as having an IS by CT or MRI and meeting the diagnostic criteria of WHO;
(3) having an initial IS within 7 days, with limb dysfunction (muscle strength of the limbs is less than 5);
(4) maintaining consciousness (NIHSS scale consciousness level 0 or 1); and
(5) having signed an informed consent form.
The exclusion criteria:
(1) blood vessels that were recanalized after thrombolysis or thrombectomy;
(2) cardiopulmonary dysfunction; a history of craniocerebral trauma, with fracture trauma or with rheumatoid arthritis; or already had a physical disability or other diseases that had an impact on the affected limb;
(3) cognitive impairment or other mental illness that prevents cooperation with researchers.
All the patients were assessed with the MBI within 24 hours of hospital admission before rehabilitation. Demographic data (age, gender, muscle strength of the limbs) were gathered from medical records.
2.2 Ethics statement
All subjects had been given written informed consent before the study, and the protocols had been approved by the human ethics committee of The Second Affiliated Hospital of Zhejiang University. All clinical investigation has been conducted according to the principles expressed in the Declaration of Helsinki.
2.3 Instrument
The MBI[17]
2.4 The Rasch model
The Rasch analysis [18]
1) each option must have 10 observations at least,
2) the unidimensionality of the scale,
3) values of item rating categories should be monotonically asymptotic,
4) outfit MnSq < 2.0,
5) the difficulty difference between adjacent categories >0.81 logits.[19]
Second, the validity was examined by assessing whether each item fits with Rasch model expectations through the mean squares (MnSq) and the easy items for patients by item hierarchy, the values of infit MnSq and outfit MnSq range from 0.5 to 1.5 were accepted.[20] [20] [21] [16] P < .05, indicated DIF.[20]
3 Result
Over the research period, 231 patients with IS were included in this study. The average age of patients was 62.3 ± 13.0 years old, and 69 (29.9%) of them were female. The average scores of muscle strength of the affected upper limbs and lower limbs were 2.3 ± 1.7 and 2.9 ± 1.5, respectively. The average score of MBI was 36.2 ± 17.8, the distribution of response for each item was shown in Table 1 .
Table 1 -
Distribution of response for each item of the MBI for ischemic stroke patients.
Item
Score
Count
Percent (%)
Feeding
0
134
58
2
48
21
5
38
16
8
5
2
10
5
2
Bathing
0
140
61
2
56
24
3
34
15
4
1
0
Grooming
0
132
57
2
50
22
3
42
18
4
6
3
5
1
0
Dressing
0
135
58
2
56
24
5
33
14
8
6
3
10
1
0
Bowels
8
7
3
10
224
97
Bladder
0
7
3
10
224
97
Toilet
0
111
48
2
67
29
5
51
22
8
2
1
Transfer
0
69
30
3
76
33
8
38
16
12
33
14
15
15
6
Walking
0
115
50
3
53
23
8
37
16
12
14
6
15
12
5
Stair
0
169
73
2
33
14
5
15
6
8
7
3
10
7
3
MBI = modified Barthel Index.
3.1 Item rating categories
The results showed that not all 10 items met the set criteria of appropriate item rating categories. Some options of the feeding, bathing, grooming, dressing, bowels, bladder, toilet, stair did not have 10 observations (Table 1 ). Average measures of the adjacent options increased not evenly, though no disordered thresholds were observed. The outfit MnSq values of other options were >2 except for the rating 2 (moderate help) and 4 (fully independent). The difficulty gap between the rating 3 (minimal help) and 4 (fully independent) was small. The item rating categories should not meet the 5 criteria, which means the rating categories were not functioning adequately in items.
3.2 Item fit with Rasch model
The infit MnSq of feeding, dressing, bowels, bladder, stairs, and walking range from 0.52 to 1.28, which in the acceptable range of 0.5 to 1.5. The infit MnSq of transfer, bathing, grooming, and toilet was 1.69, 0.33, 0.42, and 0.35, respectively. To check for the possible influence of unfit items, the analysis was repeated after the unfit items were removed. The results showed the reliability was lower. Hence, results using the complete items were presented. Error ranged from 0.03 to 0.05, which showed that the item was relatively stable in estimating the ability of the IS patients. Both Point (PT)-Measures of bowels and bladder were 0.27, which were extremely lower than PT-Measure of other items (range from 0.64 to 0.90) (Table 2 and Fig. 1 ).
Table 2 -
Item measures, fit statistics, and PT-Measure correlation for the MBI for ischemic stroke patients.
Item
Measure
Error
Infit Mnsq
Zstd
Outfit Mnsq
Zstd
PT-Measure
Feeding
0.49
0.04
0.99
0.0
0.69
−2.0
0.72
Bathing
0.78
0.05
0.33
−5.2
0.26
−4.9
0.82
Grooming
0.70
0.05
0.42
−4.6
0.47
−3.2
0.80
Dressing
0.55
0.04
0.82
−1.3
0.61
−2.5
0.72
Bowels
−1.66
0.04
0.52
−4.2
0.37
−5.0
0.27
Bladder
−1.58
0.04
0.62
−3.2
0.79
−1.3
0.27
Toilet
0.45
0.04
0.35
−7.1
0.34
−5.6
0.86
Transfer
−0.41
0.04
1.69
4.6
3.17
9.0
0.90
Walking
0.00
0.03
1.28
2.3
1.14
1.1
0.84
Stair
0.67
0.04
1.23
1.4
0.61
−2.2
0.64
MnSq = mean squares, PT-Measure = point-measure.
Figure 1: The bubble plots of item.
3.3 Construct validity
Construct validity was demonstrated by the item hierarchy (Table 2 ). Construct validity of bowels and bladder was easy for the IS patients, but the construct validity of bathing and grooming was difficult for the IS patients.
3.4 Local independence
No evidence of local dependency between items was found as the correlation coefficients between item residuals were <0.7.
3.5 Dimensionality
The first principal component was found to explain 54.2% of the variance. However, there was substantial unexplained variance (44.8%) and the first 2 contrasts had eigenvalues > 2 (4.5 and 2.3, respectively), and the possibility of the existence of additional components was examined. The 2 potential factors effect were very low, supporting unidimensionality of the scale, with the factor sensitivity ratio values of 10.8% (4.5/41.7) and 5.5% (2.3/41.7), respectively.
3.6 Person and item separation and reliability
The obtained person separation index value was 3.73, which was associated with a reliability coefficient of 0.88. Furthermore, the item separation index value was 20.87, which was associated with a reliability coefficient of 1.00.
3.7 Differential item functioning (DIF)
All DIF contrasts of gender and age were found to be less than the criterion of <0.43, and all the items were free from the substantial DIF. But not all muscle strength of the limbs were found to be less than the criterion of <0.43. The items of feeding, bathing, grooming, dressing, bowels, and bladder had DIF for upper limbs muscle strength, the items of bowels, bladder, transfer, walking, and stair had DIF for lower limbs muscle strength, the item of toilet was free from the substantial DIF. Figure 2 shows the detail about the DIF contrasts of all muscle strength of the limbs.
Figure 2: DIF contrasts for a) gender, b) age, and c) muscle strength of the limbs for the MBI.
Figure 2 (Continued): DIF contrasts for a) gender, b) age, and c) muscle strength of the limbs for the MBI.
3.8 Targeting
The matching degree of item difficulties and personability was not satisfied (Fig. 3 ), with a difference of 1.17 logics. 29.4% patients, no easy items could match their abilities, the items of MBI were difficult for disabled patients.
Figure 3: Distribution map for persons and items.
4 Discussion
In this study, the main findings were
1) The MBI was highly reliable to assess the ADL;
2) The items rating categories were not very satisfactory, which need to merge;
3) The unfit items of transfer, bathing, grooming, and toilet were worth keeping, but the items of bowels and bladder may be not suitable for IS patients;
4) All the items were free from substantial DIF for gender and age, but not all muscle strength of the limbs were found be free from substantial DIF;
5) The matching degree of item difficulties and patients ability was not satisfied, the items were difficult for IS patients.
The results of the Rasch analyses showed that the reliability for the MBI in this sample of patients with IS was good both for persons and items, with values of 0.88 and 1.00, respectively, these results indicate that scale items were validly and reliably to assess the patient’ ADL. Higher reliability represents smaller measurement error.[22]
Even the range of difficulty can be distinguished, but rating categories were not very satisfactory, with a small difficulty gap (between the rating 3 and 4). The fact is that “minimal help” represented the items could be finished, but unskilled, need somebody beside to give little assistance if needed, and “fully independent” represented to finish alone. Therefore, there was no obvious difference between minimal help and fully independence. Both of them could be finished, the little difference was whether finished it alone. Besides, the IS patients had limb dysfunction, ADL were affected, most IS patients could not finish feeding, bathing, grooming, dressing, toilet, and stair alone in the acute phase. The results suggest that options 4 and 5 of the feeding, bathing, grooming, dressing, toilet, and stair should be merged.
The research found that the items of transfer, bathing, grooming, and toilet were unfit with the Rasch Model (Table 2 ). When we removed the unfit items,[23] [24] Table 2 and Fig. 1 ), the conclusion could be that the bowels and bladder were less relevant to other items. Conceptually, the incontinence differs from other items, and the World Health Organization classifies incontinence as impaired bodily function and other items are activity restriction.[25] [17] [26]
In addition, all scale items were free from substantial DIF for gender and age, but there was a DIF effect in muscle strength of the limbs (Fig. 2 ). The items of feeding, bathing, grooming, dressing need upper limbs’ help, higher muscle strength of the limbs, easier for patients to finish the items. Whether muscle strength of the limbs >3, the degree of patient involvement was greatly different. With item toilet need the upper and lower limbs’ help, DIF contrast had no obvious difference neither upper nor lower limbs. Items of stairs, chair/bed transfers, and walking need low limbs’ help. The effect was similar to the upper limbs. The DIF contrast of items bowels and bladder had a difference between muscle strength of the limbs, which told us the scores of bowels and bladder were unstable between muscle strength of the limbs. But the muscle strength of the limbs did not affect the scores of bowels and bladder. A possible explanation was that incontinence was not associated with muscle strength of the limbs, incontinence items were not suitable for IS patients.
Examining the distribution map (Fig. 3 ), the conclusion could be that there was a mistargeting between item difficulty and personability. In 29.4% patients, the items of MBI were difficult for disabled patients. The patients with extremely disabled might have lower ability than the item difficulty, and their muscle strength of the limbs also might be too low to complete the items. Hence, the items may be cannot reflect the real ability of the disabled patients. In other words, better mobility does not represent more independence, and the total scores may not be used to disabled patients as an indicator of treatment, rehabilitation, and nursing. Further analysis may be needed to verify the finding or more easier items will need to be added to the scale. A wider range of levels for ADL could be helped to draw the conclusion.
5 Limitations
This study had some limitations. First, only the IS patients in the neurology department were included. A further multi-center study is needed. Second, the MBI was assessed by the researcher based on the ADL of the patients, which might be affected by the subjective consciousness of the researcher. Finally, the sample consisted of the IS patients with hemiplegic, and the findings of the study might not be generalized to all IS patients.
6 Conclusion
In conclusion, the MBI had high reliability but a relatively bad matching degree between item difficulty and patient ability. The items still need further improvement to reflect the activities of daily living in IS patients.
Acknowledgments
The authors are grateful for the participation of stroke patients in this research. They sincerely thank the assistance of the nursing staff in the department of neurology of The Second Affiliated Hospital, Zhejiang University School of Medicine.
Author contributions
Data curation: Jianmiao Wang, Yuanyuan Chen.
Investigation: Hui Wei, Yanqin Chen.
Methodology: Jingfen Jin, Hongyan Yang.
Software: Yuanyuan Chen.
Supervision: Jingfen Jin, Hongyan Yang.
Writing – original draft: Hongyan Yang, Yuanyuan Chen.
Writing – review & editing: Jingfen Jin.
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