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Print version ISSN 1413-3555
Rev. bras. fisioter. vol.16 no.3 São Carlos May/June 2012 Epub June 14, 2012
Lílian G. K. RiesI; Stella M. MichaelsenI; Patrícia S. A. SoaresII; Vanessa C. MonteiroII; Kátia M. G. AllegrettiII
IPostgraduate Program in Physical Therapy, Universidade do Estado de Santa Catarina (UDESC), Florianópolis, SC, Brazil
IIUniversidade Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil
BACKGROUND: The Pediatric Balance Scale (PBS) was developed from a modified version of the Berg Balance Scale aiming to obtain a balance scale more appropriate for the child population.
OBJECTIVES: To adapt the PBS into Brazilian-Portuguese and to evaluate the intra and inter-rater reliability of the Brazilian-Portuguese version of PBS.
METHODS: To perform the cross-cultural adaptation of the American version of PBS four translators were involved, who have performed two translations and their respective back-translations. Then, a review by a multidisciplinary committee and a subsequent an assessment of the equivalence of meaning between the back-translations and the original English scale were performed by 3 and 30 healthcare professionals respectively. The intra-rater reliability of the final version of the Brazilian-Portuguese PBS was evaluated using a test-retest design with one-week interval. The Brazilian-Portuguese version of the PBS was tested twice on the same day by two different raters to test the inter-rater reliability. The inter-rater reliability, which was measured from a video of the volunteers performance, was evaluated by comparing the score given by five raters independently. Reliability was evaluated by Intraclass Correlation Coefficient (ICC). Fifteen volunteers (11±2.7 years) diagnosed with Cerebral Palsy (CP) classified at level I and II on the Gross Motor Function Classification System (GMFCS) were assessed.
RESULTS: The reliability of the PBS total score for both intra-rater (ICC=0.85) and inter-rater (ICC=0.91) was excellent. The inter-rater reliability (measured from the video) for the total score was also classified as excellent (ICC=0.98).
CONCLUSION: The results showed adequate reliability for the PBS for pediatric population with CP diagnostic classified at level I and II on the GMFCS.
Keywords: cerebral palsy; balance; pediatrics; assessment; reliability; physical therapy.
Cerebral Palsy (PC) is defined as a group of permanent disorders of the development of movement and posture, which are attributed to non-progressive disturbances that occurred in the developing fetal or infant brain causing activity limitation. The motor disorders of CP are often accompanied by disturbances of sensation, perception, cognition, communication and behavior, by epilepsy and by secondary musculoskeletal problems1. The limitations of a child with CP lead to the adoption of abnormal postures and movements that interfere with the global neuromuscular development and also with the postural control mechanism2.
Although there are scales used in children with neuro-psychomotor development disoders, which the mechanism of postural control is clinically evaluated during the performance of tasks that involves the control of body balance and mobility3-5, specific scales for evaluation of mobility and balance were predominantly developed for elderly population6-8.
One of the most used scales for the evaluation of balance is the Berg Balance Scale (BBS)7, which has been translated into Portuguese by Miyamoto et al.9. This scale was originally proposed to assess balance in the elderly population, however it has recently been used in both adults with neurological impairments10 and children populations11-13.
Based on a pilot study with typically developed children, in which the BBS showed unsatisfactory test-retest reliability, Franjoine, Gunther and Taylor14 observed that most of the children tested had difficulty in maintaining the static postures. The authors of this piloty study proposed modifications in the 14 items of BBS in order to develop a balance scale more appropriate for children population. Therefore, the Pediatric Balance Scale (PBS) was developed as a modification of the BBS. In the pediatric version, the items were rearranged in a functional sequence, the time for maintaining the static postures was reduced, and the instructions and the suggested equipments were modified.
The original PBS was developed in New York, with American children, as a functional balance capacity measure of school-aged children (5-15 yrs old) with mild to moderate motor impairment. This scale has high test-retest reliability and it allows variability in the score criterion on a single item. The scale contains 14 items evaluating functional activities that a child can perform at home, at school or in the community. This scale is relatively simple and of easy administration, with total time of administration of 15 minutes14. In typically developed children, significant differences were observed on the performance of the PBS regarding age and gender, as well as the association between theirs scores with age, height, weight and body mass index15. In addition, the PBS was sensitive to changes in the functional balance in successive evaluations (with 4-month interval, during three years) of six children with mild to moderate CP16. The PBS was also linearly correlated with the Gross Motor Function Measure (GMFM) with r=0.87 (p=0.01) in a population of children with CP17. These studies used the dimensions D and E of the GMFM, which tests the child in standing position, walking, running and jumping, and they observed that the two tests complement each other.
Some authors have recommended the cross-cultural adaptation of scales and questionnaires existent in other cultures, supporting the idea that a good cultural and linguistic adaptation could facilitate the exchange of information among the scientific community18,19. Translations and adaptations of previously validated scales constitute a facilitator measure of the conduction and dissemination of health measurement18.
Reliable functional balance measures are important in the pediatric clinic as a manner of justifying an intervention or to evaluate the outcomes of interventions. To date, there are no studies carried out in the Brazilian community that used or validated the PBS. Therefore, this study aims to cross-culturally adapt the content of PBS and to evaluate the reliability of the Brazilian version for the use in the pediatric population with diagnosis of CP.
Four translators and 33 health professionals worked on the cultural adaptation of the English version of PBS14. Fifteen volunteers from the physical therapy clinic of our institution were selected to participate on the reliability of the PBS. They had the diagnosis of CP and were classified at levels I and II of the Gross Motor Function Classification System (GMFCS)20. To be included in the study the child should be able to remain in the standing position, without upper limbs support. Children with attention deficit disorder, the ones who used orthoses on the lower limbs and those with deficit in the capacity of understanding simple orders were excluded from the study.
This cross-cultural adaptation study was approved by the Ethics in Research Committee of the Universidade Federal de São Paulo (UNIFESP), Hospital São Paulo, São Paulo, SP, Brazil (nº 1109/06) and the reliability study was approved by the Ethics in Research Committee of Universidade do Estado de Santa Catarina (UDESC), Florianópolis, SC, Brazil (nº 191/2008). Everyone involved and the legal guardians of the volunteers with CP signed the informed consent term after explanations and agreed in participating in the study.
Translation and cross-cultural adaptation
The adaptation of the original English version of PBS14 was carried out according to the guidelines from Guillemin21 and Beaton et al.22, following the recommendations of the Scientific Advisory Committee of the Medical Outcomes Trust23. The translation into Portuguese was conducted by two independent Brazilian translators who were proficient in English and aware of the objectives of the study. The translation was performed independently and the translators were asked to be precise with the words, avoiding interpretations of expressions or sentences. This stage aimed at the detection of divergent errors and interpretations of ambiguous items on the part of each one of the translators, that developed a consensual version of the instrument in Portuguese.
This 1st version was back-translated into English by two independent translators, of American origin, fluent in Portuguese, and who had not participated in the previous stage. The two translators were not aware of the original version of the instrument as well as the objectives of the study. Two English versions were obtained and were reviewed by a multidisciplinary committee composed of three professionals (one medical doctor and two physical therapists), to develop the final version of PBS. This stage aimed to compare the original and final versions, using techniques structured to solve discrepancies, change the format, rejecting inappropriate terms, and to verify the equivalence of the original and final versions at the end of the process. Therefore, after the consensus, it was obtained a second version in Portuguese. The final version in Portuguese was applied to a group of 30 musculoskeletal and neurological physical therapists who answered a questionnaire related to the level of understanding of the alternatives, verifying possible doubts with regards to the terms used in the evaluation of PBS.
As well as BBS, the PBS contain 14 items and, for each one, the score ranging from 0 to 4 is used. Several items require that the volunteer maintains the position for a specific time. Progressively, more points are deduced if the time or the distance required are not met, if the volunteer's performance requires supervision or if the volunteer touches an external support or receives assistance from the examiner. The maximum score of the scale is 56, the higher the score, the better the balance. The necessary material for evaluation is described in Appendix 1. The BBS and PBS have different sequences of application of the evaluated items (Table 1).
Reliability was evaluated when the same examiner applied the scale in different days (intra-rater), when two different examiners applied the scale (inter-rater) and when different observers (inter observers) defined the score through the videos of the volunteers' performance (excluding the eventual variability of each one). Before applying the scale in children with CP, the two examiners trained its application, evaluating four typically developed children.
Thus, 15 CP participants were assessed at three time-points. The first two moments occurred with the test being applied by two independent examiners (examiner 1 and examiner 2), constituting the evaluation 1 (EV1) and the evaluation 2 (EV2). These evaluations were carried out in the same day with an interval of one hour. The third moment occurred with the evaluation of one of the previous examiners (examiner 1), repeated in a interval of one week constituting the evaluation 3 (EV3). During EV2 videos recordings were made. Five independent observers (O1-O5), without previous knowledge of the English version, received the translated PBS, the videos and the scoring sheet.
Participants characteristics were calculated through descriptive analysis. Intraclass Correlation Coefficients (ICC) and their 95% confidence intervals for the evaluation of intra-rater (EV1 x EV3) and inter-rater (EV1 x EV2) was used to evaluate the reliability. The inter-observers reliability (O1-O5), for the score of volunteers' performance based on the videos, was also evaluated using the ICC and 95% CIs. The following classification was used for interpreting the ICC values: weak reliability, ICC<0.40; moderate reliability ICC<0.75; and excellent reliability, ICC>0.7524. Data were analyzed using SPSS 17.0 for Windows and for all procedures the significance level was set at 5% (p<0.05), with two-tailed distribution.
The 1st version of PBS, in Portuguese, and the two English versions were referred to a multidisciplinary committee to be analyzed. Modifications regarding grammatical errors, which could change and delay the understanding of the items, were performed. After the committee review, alternatives have been reformulated, and some terms were substituted by other similar ones, such as "rest supported" for "remain supported", "stationary" for "static", "stands up" for "capable to be standing". At the end of this process, it was obtained the 2nd version, which was applied to 30 physical therapists. For the process of cross-cultural adaptation, it was established a confidence interval of 15% for the understood and non-understood alternatives. None of the items reached the threshold of 15% (Table 2). Therefore, it was not necessary to make modifications on the scale, and then, this was considered the final Portuguese version of PBS.
Fifteen volunteers with CP diagnosis (age=11.0±2.7 yrs, weight=33.4±9.2 kg and height=140.6±14.2 cm) participated in the reliability evaluation. Ten volunteers were classified at level I of GMFCS20, six had spastic hemiparesis CP; three had spastic diparetic and one had ataxia. Five volunteers were classified at level II, two had spastic hemiparesis and three had spastic diparetic.
Intra-rater and inter-rater reliability of the PBS
All participants scored 4 in the tasks 1-6 and 12 of PBS, and the agreement between examiners was equal to 100%. In the task 7 of PBS, only one examiner scored 3 for one of the volunteers. Due to the variability absence for the tasks 1-7 and 12, it was not possible to calculate the reliability values for them, however, as the agreement was 100%, it was attributed an ICC of 1. For the other tasks, the individual reliability of these items was calculated (Table 3). Reliability was excellent for items 9, 10, 13 and 14 and weak for item 8 (standing with one foot in front). The intra-rater agreement was equal to 100% for items 1-6 and 12, excellent for items 9, 13 and 14 and moderate for item 8.
Inter-observers reliability for the score based on videos
With regards to the item turning to look behind, three of the five observers scored 4 for all children and, in the item-retrieving object from floor, one of the observers scored 4 for all children. So, due to the absence of variability, it was not possible to calculate the ICC in these items. The other individual items, as well as the total score, showed an excellent inter-observer reliability (Table 4).
Due to the importance of detection of balance disorders, the PBS was developed for pediatric population14. For the correct balance evaluation, validated and cross-culturally adapted instrument to allow comparisons among different populations is needed. To date, this instrument was not available in Portuguese. As demosntrated on this study, the reliability of the cross-culturally adapted version into Portuguese is very similar to the original English version of PBS.
The translation and cross-cultural adaptation of instruments should follow a standardized procedure21,22. Based on the criteria defined by Scientific Advisory Committee of the Medical Outcomes Trust, the cross-cultural adaptation of an instrument involves the evaluation of conceptual and linguistic equivalences and the evaluation of psychometric properties18. In this study, both the equivalence of meanings from both cultures and the maintenance of the meaning that each task presented in the original language were performed. The small changes that were performed in agreement with the suggestions of the multidisciplinary committee resulted in a greater understanding of the instrument.
The BBS7 has been already translated and cross-culturally adapted into Portuguese and showed a intra-rater and inter-rater reliability in a sample of seniors between 65 and 82 years of 0.97 and 0.98, respectively9. The BBS was used to evaluate balance of children with typical development11 and with CP11,13. The study of Gan et al.13 used the BBS, although the PBS is mentioned, these authors considered that more evidences are necessary to support its validity. However, other study observed that balance measures in people with Friedreich's Ataxia were not well documented, suggesting more studies to determine the most appropriate instrument, considering the possibility to use the PBS in this population25.
The participants of this study had difficulty to stand in one foot and to reach forwards. A third of the children were unable to sustain for 3 seconds in one foot. In order to to reach forwards, they needed supervision or reached less than 12.5 cm.
The study that developed the PBS observed a good reliability when it was used in school-aged children with mild and moderate motor impairments14. The sample of 20 children included eight children with diagnosis of spastic diplegia and two with hemiplegia, and the ICC values were 0.99 for both intra-rater and inter-rater reliability. In the present study, with volunteers between 7 and 15 years old with a diagnosis of CP, classified at the levels I and II of GMFCS, both the intra-rater and the inter-rater reliability of PBS were also high.
The PBS was also used to evaluate and to describe the functional balance of older typically developed children, newer typically developed children, children with ataxic CP and children with spastic CP26. In eight children with CP (four spastic and four ataxic) of this study, aged between 10 and 14 years and levels of GMFCS between I and III, the mean score of PBS was 47.2±9.5 for the spastic and 48.5±6.24 for the ataxic, lower than the ones of the present study. In the present study, volunteers had a total score that ranged between 46 and 56 points in the PBS, and the volunteers with spastic CP had a score of 52.1±3.1, and the only volunteer with ataxic CP had the score of 53 points. The lowest score of the mentioned study26 is attributed to the greater impairments of the evaluated children, one spastic and two ataxic were classified at level III of GMFCS.
It was verified in the present study that although both intra-rater and inter-rater reliabilities have been high, the intra-rater reliability slightly lower than the inter-rater reliability. Considering that, for the intra-rater reliability (EV1 x EV3), the evaluation was performed on different days and, for the inter-rater (EV1 x EV2), on the same day, the presence of variability in the behavior of the evaluated children on different days should be considered. This finding is reinforced when the variability due to the child's performance is eliminated in the reliability based on videos. When different observers scored the children's performance, the reliability of scale shows an ICC higher than the ones of intra and inter-rater reliability.
When the reliability of individual items was evaluated, it was observed that the task of standing with one foot in front had a lower, but still appropriate intra and inter-rater reliability. Still, in the task turning to look behind although the means were similar (3.9 points for the three evaluations and ranging between 3.8 and 4.0 points for observers 1 to 5), the ICC was not significant in none of the evaluated reliability conditions. It is possible that the observers have been influenced by the interpretation of the BBS, in which the score is given predominantly considering the weight transfer between the lower limbs and not the trunk rotation, such as in the PBS. It is important that the examiners, who have knowledge of the BBS, when using the PBS, be aware of such difference. In the original English version of PBS, the test-retest reliability of this item achieved Kappa coefficient of 0.93.
It was observed that for the studied sample, the total scores for balance were high and that, in several tasks all participants reached the maximum score of 4 points. As reported for the BBS27, the PBS presented a ceiling effect on 7 items. For futures studies, a simplified version of PBS should be considered in the evaluation of children with CP classified at levels I and II of GMFCS.
Reliable functional balance measures are important in the pediatric clinic for measuring the effects of interventions. The results showed appropriate reliability for PBS in children with diagnosis of CP classified at levels I and II of GMFCS. Thus, the translation into Portuguese of PBS, as well as the demonstration of its intra-rater reliability when different examiners apply the scale or observe the performance based on videos, should contribute as a facilitator alternative of the balance evaluation of the Brazilian pediatric population with diagnosis of CP.
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Lílian Gerdi Kittel Ries
PPG Fisioterapia, CEFID/UDESC
Rua Pascoal Simone, 358, Bairro Coqueiros
Florianópolis, SC, Brasil, CEP 88080-350
e-mail: lílian.firstname.lastname@example.org; email@example.com