ANUMBER OF STUDIES have documented the neurobehavioral

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1 ORIGINAL ARTICLE The Pediatric Quality of Life Inventory: An Evaluation of Its Reliability and Validity for Children With Traumatic Brain Injury Melissa L. McCarthy, ScD, Ellen J. MacKenzie, PhD, Dennis R. Durbin, MD, MS, Mary E. Aitken, MD, MPH, Kenneth M. Jaffe, MD, Charles N. Paidas, MD, Beth S. Slomine, PhD, Andrea M. Dorsch, PhD, Ronald A. Berk, PhD, James R. Christensen, MD, Ru Ding, MS, and the CHAT Study Group 1901 ABSTRACT. McCarthy ML, MacKenzie EJ, Durbin DR, Aitken ME, Jaffe KM, Paidas CN, Slomine BS, Dorsch AM, Berk RA, Christensen JR, Ding R, and the CHAT Study Group. The Pediatric Quality of Life Inventory: an evaluation of its reliability and validity for children with traumatic brain injury. Arch Phys Med Rehabil 2005;86: Objectives: To assess the reliability and validity of the Pediatric Quality of Life Inventory, version 4.0 (PedsQL), and to compare it with that of the Behavior Rating Inventory of Executive Function (BRIEF) among children with traumatic brain injury (TBI). Design: Prospective cohort study that documented the health-related quality of life of 391 children at 3 and 12 months postinjury. Setting: Four level I pediatric trauma centers. Participants: Children (age range, 5 15y) hospitalized with a TBI or an extremity fracture. Interventions: Not applicable. Main Outcome Measures: Parent-reported PedsQL and BRIEF scale scores. Results: Both the PedsQL and BRIEF scales showed good internal consistency (PedsQL range,.74.93; BRIEF range,.82.98) and test-retest reliability (PedsQL r range,.75.90; BRIEF r range,.82.92), respectively. Factor analysis revealed that most PedsQL items loaded most highly on their conceptually derived scale. The PedsQL cognitive function From the Departments of Emergency Medicine (McCarthy, Ding) and Physical Medicine and Rehabilitation and Pediatrics (Christensen), Johns Hopkins University School of Medicine, Baltimore, MD; Center for Injury Research and Policy, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD (MacKenzie); Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA (Durbin); Department of Pediatrics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR (Aitken); Departments of Rehabilitation Medicine and Pediatrics, Children s Hospital and Regional Medical Center and University of Washington School of Medicine, Seattle, WA (Jaffe); Department of Surgery, University of South Florida, Tampa, FL (Paidas); Department of Neuropsychology (Slomine) and Pediatric Rehabilitation Medicine (Christensen), Kennedy Krieger Institute, Baltimore, MD; Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD (Slomine); Division of Rehabilitation Psychology, Children s Hospital and Regional Medical Center and University of Washington School of Medicine, Seattle, WA (Dorsch); and Johns Hopkins School of Nursing, Baltimore, MD (Berk). Presented as a poster at the World Injury Conference, June 7, 2004, Vienna, Austria. Supported by the National Center for Injury Prevention and Control of the Centers for Disease Control and Prevention (grant no. R49/CCR319701). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Melissa L. McCarthy, ScD, 1830 E Monument St, Ste 6-111, Baltimore, MD 21205, mmccarth@jhmi.edu /05/ $30.00/0 doi: /j.apmr scale detected the largest differences among groups of children with varying severities of TBI as well as parents assessment of change in cognition postinjury. Conclusions: Although the reliability of the 2 instruments is comparable, the PedsQL discriminates better among children with TBI. The PedsQL is a promising instrument for measuring the health of children after TBI. Key Words: Brain injuries; Pediatrics; Quality of life; Rehabilitation by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation ANUMBER OF STUDIES have documented the neurobehavioral consequences of traumatic brain injury (TBI) in children, but few have examined its impact on a child s functional status, role performance, and emotional well-being Generic measures of health status complement the more traditionally used clinical end points because they measure outcome from the patient s perspective and reflect several dimensions of health, including physical function and psychologic well-being. Furthermore, they can be self-administered or administered over the telephone, providing practical assessments of outcome. 11 The literature is replete with health status measures designed for adults. However, it is largely during the past decade that a number of health status instruments have been developed for children that are comprehensive, standardized, and relevant to the injury population One of the most promising is the Pediatric Quality of Life Inventory, version 4.0 (PedsQL). The PedsQL is a generic, health-related quality of life (HRQOL) instrument developed to measure the core dimensions of physical, mental, and social health, as well as role (school) function. 20,21 It was designed for use with different pediatric populations regardless of age, disease, or type of medical treatment. The PedsQL has several advantages over other health-status instruments. First and foremost, the PedsQL is a flexible instrument. The PedsQL advocates a modular strategy. Disease-specific modules can be integrated with the generic scales so that health domains germane to a specific condition can be more sensitively measured. Second, the PedsQL covers a wider spectrum of health than some other instruments, such as the WeeFIM instrument, the Pediatric Evaluation and Disability Inventory, or the Functional Status II(R), that were developed to measure the health of children with more severe, chronic health conditions Third, the PedsQL is easy to administer over the telephone. The items are relatively short and the response set is the same for all of the core scales in contrast to other instruments. 12,17,18 Finally, there are versions of the PedsQL that have been developed for infants and tod-

2 1902 USE OF PedsQL IN TRAUMATIC BRAIN INJURY, McCarthy dlers as well as self-reported (child) forms for children aged 5 and older. Although this study was limited to parent-proxy reports of children who were 5 years and older at the time of injury, this is an important advantage for future research and surveillance efforts. The purpose of this study was to examine the reliability and validity of the PedsQL for children hospitalized with TBI. Because cognitive dysfunction is the most important impairment after TBI, we supplemented the PedsQL generic instrument with a PedsQL cognitive function scale. 22 This 6-item scale was initially developed as part of a multidimensional fatigue scale and showed good discriminant validity among children with and without cancer. To validate the PedsQL cognitive function scale for children with TBI, we compared the reliability and validity of the PedsQL (with and without the cognitive function scale) with that of the Behavioral Rating Inventory of Executive Function (BRIEF), a standardized, validated instrument designed to assess executive function among children with a wide array of health conditions, including TBI. 23,24 Executive function refers to a multidimensional set of abilities that are responsible for guiding cognitive, emotional, and behavioral functions, particularly during goal-directed activities. 23 Although there is no uniform definition of executive function, commonly agreed-on elements of executive function include the ability to initiate actions or ideas, plan and organize tasks, shift one s thoughts or attention, resist inappropriate impulses, monitor and evaluate one s behavior, and retain information actively in memory when solving problems. 25,26 METHODS Study Population Children between the ages of 5 and 15 years who were hospitalized for 1 or more nights at 1 of 4 level I pediatric trauma centers for treatment of a TBI or an extremity fracture were eligible for the Children s Health After Trauma (CHAT) study. Children with an extremity fracture as well as children with varying severities of a TBI were included in the study to facilitate the validation of the PedsQL and BRIEF scales. We expected there to be differences in the health profiles of children with a fracture when compared with children with a TBI. We also expected children with a more severe TBI to have a different health profile than children with a less severe TBI. All children with a TBI had a head Abbreviated Injury Scale (AIS) score between 2 and 5 and all children with an extremity fracture had an extremity AIS score of 2 or greater. Although all study subjects could have associated injuries, eligible children with an extremity fracture could not have any evidence of a TBI (ie, head AIS score, 0; Glasgow Coma Scale score, 15; normal neurologic findings and no documented loss of consciousness, confusion, disorientation, dizziness, or posttraumatic amnesia at the scene or on hospital admission). Children were excluded if they (1) or their parents did not speak English; (2) had a major preexisting psychiatric (eg, schizophrenia or bipolar disorder), physical (eg, amputation or cerebral palsy), or cognitive disorder (eg, mental retardation or prior TBI-related hospitalization); (3) were a suspected case of child abuse; or (4) died during the initial hospitalization. To ensure adequate numbers of subjects with more severe TBI, the sample was stratified by AIS severity. The sampling strategy was devised to enroll relatively equal numbers (n 95) of children with a maximum head severity of 0 (extremity fracture and no TBI), 2, 3, or 4. Because fewer children sustain a head AIS injury of 5 (severe), the target number for that group was approximately half (50) of the other study groups. Procedures This study was approved by the institutional review boards of all 4 participating institutions. Between January 15, 2002, and July 31, 2003, study coordinators at the 4 participating institutions identified 541 eligible children and 491 (91%) families agreed to participate. Consenting families were contacted by a survey research firm that was responsible for conducting all telephone interviews with the parent or guardian of the injured child. Of the 491 who consented, 433 (80% of all eligible subjects) families completed a baseline interview that occurred within 3 weeks of the initial hospitalization (median, 13d). The purpose of the baseline interview was to obtain a preinjury assessment of the children s health and to determine background information on them and their families. At 3 and 12 months postinjury, the family respondent was contacted again to complete a follow-up telephone interview. The follow-up interviews measured the child s health and cognitive function postinjury as well as the respondent s assessment of the child s change in health since the injury. After the 12-month interview, the respondents of a subgroup of 95 subjects who sustained a TBI were interviewed again within a short period of time (median, 8d) to examine the test-retest reliability of the PedsQL and BRIEF. Medical record data were abstracted to ascertain the external cause of the injury as well as the nature and severity of all injuries sustained using the AIS. The AIS is the most widely used anatomic measure of injury severity. 27 The AIS classifies over 2000 injuries and rates the severity of each on an ordinal scale from 1 (minor) to 6 (unsurvivable). 28,29 We used the New Injury Severity Score (NISS) to characterize overall injury severity. 30 The NISS is calculated by summing the squares of the 3 most severe injuries sustained according to the AIS. NISS scores range from 0 to 75, higher scores connote more severe injuries. 30 Measures General health and cognitive function were measured using the PedsQL and the BRIEF. Both instruments were administered to the parent or guardian during the telephone interviews and took approximately 6 and 8 minutes to complete, respectively. The current PedsQL, version 4.0, consists of a 23-item generic core that measures children s health in the following 4 domains: (1) physical functioning (8 items); (2) emotional functioning (5 items); (3) social functioning (5 items); and (4) school functioning (5 items). The individual scales can be combined to yield 3 summary measures of physical (same as physical functioning scale), psychosocial (emotional, social, and school functioning scales), and total health (all 4 scales). 21 Scale scores range from 0 to 100; higher scores connote better HRQOL. A growing number of studies have shown the reliability and validity of the PedsQL as a measure of general physical and psychosocial health in children In addition to the generic scales, respondents also completed the PedsQL cognitive functioning scale (6 items), which has the same response format and scoring approach as the generic PedsQL scales. 22 The PedsQL cognitive functioning scale was developed as part of a PedsQL Multidimensional Fatigue Scale for pediatric cancer patients. The scale was designed based on the developers research and clinical experiences in pediatric cancer, a review of existing literature on fatigue in adult and pediatric cancer patients, feedback from focus groups, item generation, cognitive interviewing, pretesting, and field testing of the new instrument. 22 We chose to use the 6-item cognitive fatigue scale that is part of the multidimensional instrument as our measure of cognitive functioning in this study because the

3 USE OF PedsQL IN TRAUMATIC BRAIN INJURY, McCarthy 1903 items reflected aspects of cognitive functioning known to be affected by a TBI (ie, memory, attention, processing speed). The BRIEF was developed by Gioia et al 23 to assess executive function behaviors of children between the ages of 5 and 18 years. The BRIEF clinical scales consist of 72 items that measure 8 domains of executive function: (1) inhibit 10 items related to impulse control; (2) shift 8 items related to ability to change focus; (3) emotional control 10 items related to modulating emotional responses; (4) initiate 8 items related to initiating activities or ideas; (5) working memory 10 items related to holding information in mind; (6) plan/organize 12 items related to organizing task demands; (7) organization of materials 6 items related to orderliness; and (8) monitor 8 items related to self-evaluation of performance/behavior. These 8 clinical scales form 2 broader indices, behavioral regulation (first 3 subscales) and metacognition (last 5 subscales) as well as an overall score, the global executive composite (GEC; all 8 subscales). The possible range of the BRIEF raw scale scores varies depending on the number of items within the scale. However, higher scores reflect more dysfunction. Initial studies conducted with the BRIEF suggest that it is a reliable and valid measure of executive functioning in children. 23,25,39-41 In addition to the PedsQL and BRIEF, change in cognitive function was assessed by asking all respondents to compare their child s present ability to think, concentrate, remember things, and solve problems with that before the injury. Responses were categorized as same as before the injury, somewhat worse now than before the injury, or much worse now than before the injury. Data Analysis Because the findings with respect to reliability and validity were similar at 3 and 12 months postinjury and greater health differences by type of injury were observed at 3 months than at 12 months, only the results of the 3-month data are presented (with the exception of the test-retest reliability, which was only collected 12mo postinjury). However, the 12-month results are noted. For both the PedsQL and BRIEF, if an item was not completed, we used the mean of the remaining items so that the scale score could be computed if at least half of the items in the scale were completed. 21 For the PedsQL, imputation of at least 1 scale item response was required for 0.3% (emotional functioning) to 18% (total PedsQL) of scale scores. For the BRIEF, imputation of at least 1 scale item response occurred for 1% (emotional control) to 31% (global executive composite) of the scale scores. To examine the reliability of the PedsQL and BRIEF, the internal consistency of each scale was assessed using the Cronbach coefficient. 42 We hypothesized that all of the PedsQL and BRIEF scores would meet the minimum standard needed for group comparisons (ie,.70). 43 We also hypothesized that the BRIEF scales would be more likely to meet the standard recommended for comparing individual patient scale scores (ie,.90) because most BRIEF scales have more items than the PedsQL scales and internal consistency is favorably influenced by more items as long as the items are comparable. 44 The test-retest reliability of the PedsQL and BRIEF scales was evaluated by computing a Pearson product-moment correlation coefficient for each scale obtained by the first versus second 12-month interview as well as by calculating the mean difference in scale scores between the 2 interviews. We hypothesized that the test-retest reliabilities of the PedsQL cognitive function scale and BRIEF scales would be similar. To examine the construct validity of the PedsQL, the factor structure was first examined using principal components analysis with oblique rotation. An eigenvalue of 1.0 or greater was used to determine how many factors to retain. We hypothesized that among children with TBI, the empirical structure of the PedsQL would deviate from the conceptual one in the same way as previously reported by Varni et al. 21 More specifically, 5 factors would emerge from the 4 generic core scales and not all items would load highest on their respective scale. Second, the relation between the PedsQL and BRIEF scales was assessed using a Pearson product-moment correlation coefficient. We hypothesized that the PedsQL scales that measured cognitive and emotional health domains would be moderately (ie,.30 r.50) to strongly (ie, r.50) correlated with the BRIEF scales. 45 Finally, the discriminant validity of the PedsQL and BRIEF was evaluated by comparing each instrument s ability to detect significant differences among groups of subjects that were expected to vary in outcome. The first criterion was maximum head AIS severity. Children with more severe TBI were hypothesized to have worse HRQOL and cognitive dysfunction than children with less severe or no TBI. Further, we expected the largest differences among the groups to be reflected by the scales that measured cognitive dysfunction (in particular the BRIEF scales and to a lesser extent the PedsQL cognitive function scale). Because the PedsQL and BRIEF scale scores of children with head AIS 2 and head AIS 3 were similar, these 2 groups were combined so that the head severity groups consisted of head AIS score of 0 (extremity fracture and no TBI), head AIS score of 2 to 3, head AIS score of 4, and head AIS score of 5. The second criterion used to examine discriminant validity was the respondent s assessment of the child s change in cognition since the injury. Again, we hypothesized significant differences in HRQOL and cognitive dysfunction among the 3 groups (ie, same, somewhat worse, much worse now than before the injury) and we also expected the largest differences to be noted by the scales that measured cognitive function. For each comparison, 1-way analysis of variance (ANOVA) was performed. The greater the F statistic from the ANOVA, the better the scale is at discriminating among the groups. The relative validity (RV) of each scale was estimated by computing the ratio of pairwise F statistics (F for each comparison scale divided by the F statistic for the most valid scale). The RV estimates reflect how valid each scale is in terms of measuring a particular criterion in relation to the most valid scale. 46,47 RESULTS Demographics of the Study Population At 3 months postinjury, the parents/guardians of 391 (90%) of the 433 enrolled families completed the follow-up interview (median, 97d). Most of the respondents were either the biologic mother (81%) or father (12%). Subjects were more likely to be male (68%), white (70%), with an average age standard deviation (SD) of years (table 1). The children were primarily covered by commercial insurance (73%) or medical assistance (26%) at the time of injury. There were no significant differences in the sociodemographics of the children with a TBI compared with the children with an extremity fracture. However, the groups did differ significantly by injury-severity characteristics. Children with a TBI were more likely to have also sustained injuries to other parts of the body. The mean NISS for children with a TBI was 19.6 versus 6.8 for children with an extremity fracture (P.001). Traffic-related injuries were significantly more likely to have occurred among children with a TBI (37.7%) than children with an extremity fracture

4 1904 USE OF PedsQL IN TRAUMATIC BRAIN INJURY, McCarthy *P.05. P.001. Table 1: Frequency Distribution of Selected Patient and Injury Characteristics of CHAT Sample Characteristic Overall (N 391) TBI (n 302) Fractures (n 89) Age, y (%) Sex (%) Male Female Race (%) White Nonwhite Health insurance (%) Medicaid/none Commercial Average total PedsQL score preinjury SD Average BRIEF GEC score preinjury SD Hospital disposition (%)* Home Rehabilitation facility NISS (%) Mechanism of injury (%) Traffic related Fall Sports Hit by structure, object, or person All-terrain vehicle, dirt bike Other (19.1%). Finally, the vast majority of children who were discharged to a rehabilitation facility had sustained a TBI. Reliability At 3 and 12 months postinjury, the internal consistency reliability of the PedsQL (range at 3mo,.74.93; range at 12mo,.80.92) and BRIEF (range at 3mo,.82.98; range at 12mo,.84.98) scales was good to excellent as estimated by the Cronbach coefficient. All of the PedsQL and BRIEF scales are reliable enough for group comparisons. However, only the PedsQL total scale score met the reliability criterion recommended for individual patient scale scores (ie,.90) whereas 7 of the 11 BRIEF scales (including the 3 summary scales) did at both 3 and 12 months postinjury. Both instruments yielded good test-retest reliability. The Pearson productmoment correlation coefficients ranged from.75 to.90 and from.82 to.92 for the PedsQL and BRIEF scales, respectively, between the 2 time periods. In addition, the largest mean differences in scale scores within the relatively short time period was.24 for the PedsQL (psychosocial function) and.12 for the BRIEF (global executive composite). Construct Validity Table 2 lists the results of the factor analysis of the PedsQL generic core and cognitive functioning items. Five factors emerged. Two physical functioning items loaded more highly with emotional function and 2 social functioning items loaded more highly with physical functioning compared with their conceptualized scales. The only difference between the factor analysis at 3 and 12 months postinjury was that 1 of the physical functioning items that loaded most highly on emotional functioning at 3 months (ie, having hurts or aches ) was split almost equally between physical (factor loading,.293) and emotional functioning (factor loading,.285) at 12 months postinjury. The school functioning items split between 2 factors, namely, school functioning and cognitive functioning. All 6 cognitive functioning items loaded most highly with cognitive functioning. When the factor analysis was performed without the cognitive functioning items, the results were the same except that the first 3 items of school functioning all loaded highly on a separate cognitive construct (.75.81) rather than on school functioning (.12 to.25) (data not shown). There was significant overlap between the cognitive functioning items of the PedsQL and the first 3 school functioning items. The lowest correlation between a cognitive functioning item and 1 of the first 3 school functioning items was.41 (P.001) and the highest was.74 (P.001) (data not shown). Table 3 provides the Pearson product-moment correlation coefficients between the PedsQL and BRIEF scales at 3 months postinjury. As expected, the PedsQL cognitive functioning scale was moderately to strongly correlated with the BRIEF scales. The PedsQL cognitive functioning scale was more strongly associated with the BRIEF scales related to metacog-

5 USE OF PedsQL IN TRAUMATIC BRAIN INJURY, McCarthy 1905 Table 2: PedsQL Factor Loadings for Core PedsQL and Cognitive Function Items 3 Months Postinjury Among CHAT Sample PedsQL Scale/Item Factor 1 (CG) Factor 2 (PF) Factor 3 (EF) Factor 4 (SF) Factor 5 (SC) Physical functioning (PF) Difficulty walking more than 1 block Difficulty running Difficulty participating in sports/exercises Difficulty lifting something heavy Difficulty taking shower/bath by self Difficulty doing chores around house Having hurts or aches Low energy level Emotional functioning (EF) Feeling afraid or scared Feeling sad or blue Feeling angry Trouble sleeping Worrying about what will happen Social functioning (SF) Trouble getting along with peers Other kids not wanting to be friends Getting teased Difficulty doing things peers do Difficulty keeping up with others School functioning (SC) Paying attention in class Forgetting things Keeping up with schoolwork Missing school, not feeling well Missing school, going to doctor/hospital Cognitive functioning (CG) Difficulty keeping attention on things Difficulty remembering what people said Difficulty remembering what he just heard Difficulty thinking quickly Difficulty remembering what he was just thinking Difficulty remembering more than 1 thing at a time Eigenvalues Percentage variance NOTE. Rotated factor loadings of.40 are in bold. nitive abilities (range,.35 to.78) than those measuring behavioral regulation (range,.48 to.55). The PedsQL school functioning scale displayed a similar relationship to the BRIEF scales as did the PedsQL cognitive functioning scale; however, the associations were more modest. At 12 months postinjury, the correlations between the PedsQL and BRIEF scales were similar, but higher. For example, at 12 months postinjury, the PedsQL cognitive functioning scale was also most highly correlated with the same BRIEF scales as 3 months postinjury: (1) working memory (.83), (2) metacognition (.78), and (3) global executive composite (.78). When examining the relative validity of the PedsQL and BRIEF scales by head AIS severity, the PedsQL cognitive functioning scale discriminated the best among the children with extremity fractures (head AIS score, 0) and children with varying levels of TBI severity (head AIS score, 2 5) (table 4). The next most discriminant scales were the PedsQL physical (RV 75%) and school functioning (RV 68%) scales followed by the BRIEF working memory scale (RV 56%). When the individual items of the PedsQL cognitive functioning scale and the BRIEF working memory scale were compared among the head AIS groups, 8 of the 10 BRIEF working memory items yielded a relative validity (RV range, 20% 61%) that was considerably lower than all of the PedsQL cognitive functioning items (RV range, 76% 100%) (data not shown). Interestingly, the second most discriminant PedsQL item by head AIS severity was difficulty thinking quickly, a concept that is not measured by the BRIEF. Similar results were found when the sample was characterized according to the respondent s assessment of the child s change in cognition from before the injury (table 5). The PedsQL cognitive functioning scale was the most discriminant scale followed by the BRIEF working memory scale (RV 75%). Furthermore, with the exception of 1 BRIEF working memory item (RV 82%), all other working memory items yielded a relative validity that was poorer (RV range, 40% 59%) than the 6 cognitive functioning items (RV range, 72% 100%) (data not shown). The most discriminant item by respondent s assessment of child s change in cognition was the PedsQL cognitive functioning item, difficulty thinking quickly.

6 1906 USE OF PedsQL IN TRAUMATIC BRAIN INJURY, McCarthy Table 3: Pearson Product-Moment Correlation Coefficients for PedsQL and BRIEF Scale Scores 3 Months Postinjury (n 386) PedsQL Scales BRIEF Scales Physical Emotional Social School Psychosocial Health PedsQL Total Cognitive Inhibit.13* Shift Emotional control Behavioral regulation index Initiate Working memory Plan/organize Organization of materials Monitor Metacognition index Global executive composite NOTE. PedsQL or BRIEF scale scores could not be computed for 5 subjects due to missing data. Correlation coefficients of.50 are in bold. *P.05. P.001. At 12 months postinjury, the discriminant validity results of the PedsQL and BRIEF scales by head AIS severity and parents assessment of change in cognition were the same except that, after the PedsQL cognitive functioning scale, the relative validity of the next most discriminant scales was quite similar to one another. For example, at 12 months postinjury, following the PedsQL cognitive functioning scale, the next most discriminant scales had a similar relative validity: (1) BRIEF working memory RV was equal to 53%; (2) BRIEF shift RV was equal to 51%; (3) PedsQL total scale RV was equal to 47%; and (4) PedsQL physical functioning scale RV was equal to 45%. It is not surprising that there was more discrimination among the scales earlier on when the impact of the injury was largest. As time passes and subjects recover, their functional abilities are no longer as different from one another as early on. DISCUSSION The results of our study suggest that the PedsQL is a reliable measure of general health among children who sustain a TBI and/or an extremity fracture. All of the PedsQL and BRIEF scales showed adequate internal consistency reliability for group comparisons. Although most of the BRIEF scales also met the reliability criterion recommended for individual patient scores, only the PedsQL total scale did so. However, all of the PedsQL scales except for physical functioning have fewer items than the BRIEF scales. In fact, the internal consistency reliability of the 8-item PedsQL physical functioning scale was Scale* Table 4: Mean Raw Scores of PedsQL and BRIEF Scales by AIS Severity of Head Injury (n 386) Head AIS Score of 0(n 88) Head AIS Score of 2 3 (n 163) Head AIS Score of 4(n 96) Head AIS Score of 5(n 39) F Statistic RV (%) PedsQL Physical functioning Emotional functioning Social functioning School functioning Psychosocial health summary scale PedsQL total scale score Cognitive functioning BRIEF Inhibit Shift Emotional control Behavioral regulation index Initiate Working memory Plan/organize Organization of materials Monitor Metacognition Global executive composite NOTE. PedsQL or BRIEF scale scores could not be computed for 5 subjects due to missing data. *For the PedsQL, higher scores reflect better function, whereas for the BRIEF, higher scores connote poorer function. P.05. P.001.

7 USE OF PedsQL IN TRAUMATIC BRAIN INJURY, McCarthy 1907 Table 5: Mean Raw Scores of PedsQL and BRIEF Scales by Parents Assessment of Change in Cognition (n 386) Scale* Same (n 274) Somewhat Worse (n 85) Much Worse (n 27) F Statistic RV (%) PedsQL Physical health summary scale Emotional functioning Social functioning School functioning Psychosocial health summary scale PedsQL total scale Cognitive functioning BRIEF Inhibit Shift Emotional control Behavioral regulation index Initiate Working memory Plan/organize Organization of materials Monitor Metacognition Global executive composite NOTE. PedsQL or BRIEF scale scores could not be computed for 5 subjects due to missing data. *For the PedsQL, higher scores reflect better function, whereas for the BRIEF, higher scores connote poorer function. P.05. P.001. comparable (.89) to the 3 BRIEF scales with the same number of items (range,.82.86). Furthermore, the internal consistency reliabilities shown in this clinical sample were similar or slightly higher than the reliabilities reported among parentreported normative samples by the developers of the PedsQL (.75.90) and BRIEF (.81.98). 22,23 Both the PedsQL and the BRIEF had good test-retest reliability within a short period of time (average interval, 9d) as shown by the strong correlations and the small average differences between the scale scores of the 2 time periods. With the exception of the PedsQL emotional functioning scale, all of the test-retest correlations of the PedsQL and BRIEF scales were.80 or greater, which is similar to other scales that measure stable traits. 44 This is not surprising given that emotional functioning is a less stable phenomenon over a short interval than other dimensions of health. The test-retest reliabilities of the BRIEF scales in this study population were slightly higher than those reported by Gioia et al 23 for a parent normative subsample (range,.76.85) as well as a parent-reported clinical subsample (range,.72.84). To our knowledge, this is the first study to report the test-retest reliability of the PedsQL. The factor analysis of the PedsQL revealed that the cognitive function scale is the purest of the PedsQL scales. All 6 items loaded most highly on 1 factor, cognitive functioning. Three of the 4 generic PedsQL core scales (physical, social, and school functioning) included 2 to 3 items that did not load most highly on their respective scale. These discrepancies between the theoretical and empirical structure of the core PedsQL scales complicate their interpretation. School functioning was the most problematic of the PedsQL scales. Similar to that reported by Varni et al, 21 our principal component analysis yielded 5 factors rather than the 4 hypothesized because the school functioning items were split between 2 factors. The first 3 items of the school functioning scale (ie, paying attention in class, forgetting things, keeping up with schoolwork ) appeared to be measuring cognitive function whereas the last 2 items ( missing school because not feeling well, missing school to go to doctor or hospital ) seemed to be measuring role disability. Unlike our analysis of the Medical Outcomes Study 36-Item Short-Form Health Survey among adult trauma patients, in which the addition of cognitive functioning items yielded a unique factor, the addition of the cognitive functioning items to the PedsQL core scales did not result in the identification of another domain of health. Instead, the cognitive functioning items were loading highly on the same factor as several of the school functioning items. 48 These results suggest that the PedsQL school functioning items should be split into 2 separate scales. Also consistent with Varni s results, the principal-components analysis revealed that 2 of the other PedsQL scales were not pure measures of physical or social functioning. The last 2 items of the PedsQL physical functioning scale loaded highly on emotional functioning and the last 2 items of social functioning loaded highly on physical functioning. Although the items having hurts or aches and low energy level were included in the physical functioning scale, our results suggest that any differences in these items were interpreted by respondents as reflecting psychologic distress rather than a somatic expression of physical illness. Finally, our results suggest that differences in the last 2 items of the social functioning scale, difficulty doing things peers do and difficulty keeping up with others, were largely attributed to problems with physical as opposed to psychosocial health. Although we expected that the PedsQL cognitive functioning scale would be the most discriminant among the PedsQL scales, we were surprised that it outperformed the BRIEF among children with TBI. Although the BRIEF is focused on executive functioning rather than multiple domains of cogni-

8 1908 USE OF PedsQL IN TRAUMATIC BRAIN INJURY, McCarthy tion, executive dysfunction is commonly observed after TBI. Because executive functions relate to the highest levels of cognition, they regulate other cognitive processes as well as emotional responses and behavior. Furthermore, the PedsQL and the BRIEF (especially the BRIEF working memory scale) appeared to be measuring some of the same aspects of cognition, namely working memory and attention. This is supported by the strong correlation noted in this study between the PedsQL cognitive functioning scale and the BRIEF working memory scale (ie, r.78). Although the BRIEF working memory scale did a better job of discriminating among groups categorized by respondents global assessment of change in children s cognition (RV 75%) than did head AIS severity (RV 56%), it still did not perform as well as the PedsQL cognitive functioning scale. The global assessment of change question asked the respondent about different aspects of a child s cognition (ie, ability to think, concentrate, remember things, and solve problems). A key component of executive functioning is problem solving and this aspect of cognition is not measured by the PedsQL cognitive functioning scale but is measured by the BRIEF. Given that the BRIEF is a broader measure of cognition than the PedsQL and that executive functions relate intimately with higher cognitive processes, we expected the BRIEF scales to discriminate better by this criterion. It could be that the BRIEF did not discriminate as well among children with TBI because it measures a wide array of executive functioning skills that may not be as relevant to TBI. The working memory scale was the only BRIEF scale that did a reasonable job at discriminating among children with varying severities of TBI as well as among groups of children whose cognition had changed according to parent report. Both the PedsQL cognitive functioning scale and the BRIEF working memory scale tap attention and working memory. In addition, the PedsQL cognitive functioning scale measures declarative memory (ie, remembering what people told him) and processing speed (ie, thinking quickly). Problems with declarative memory and processing speed may be more specific to TBI of all severities in contrast to executive dysfunctions, which can result from many different health conditions. Interestingly, the few other studies that have used the BRIEF among children with TBI have noted a linear trend by TBI severity but not significant differences in BRIEF scale scores among groups of children with different severities of TBI. 23,40 The findings of this study must be considered in the context of the following limitations. First, the generalizability of the study s results is limited to children who were hospitalized for treatment of a TBI or an extremity fracture; these findings cannot be generalized to children who sustain milder injuries (ie, not requiring hospitalization) or to children with other types of injuries (ie, chest, abdominal, or spinal injuries). Second, we did not evaluate the reliability and validity of the child-reported version of the PedsQL. Although we cannot expect perfect concordance between child and parent ratings of HRQOL, especially among children with a neurologic injury such as TBI, it is important to evaluate the PedsQL child self-report version. CONCLUSIONS Whereas the reliability of the PedsQL and the BRIEF was comparable, the PedsQL was more sensitive to differences in cognitive function and HRQOL among children hospitalized with different types and severities of TBI. In addition, its brevity and ease of administration make it well-suited for surveillance as well as clinical and survey research. Our results suggest that some of the core PedsQL scales may need refinement to better reflect unique dimensions of HRQOL. For children with cognitive problems, we recommend splitting the school functioning scale items into 2 separate scales as well as supplementing the core scales with the PedsQL cognitive functioning scale. Despite these shortcomings, the results of our reliability and validity evaluation suggest that the PedsQL is a promising instrument for measuring the health and well-being of children with TBI. Acknowledgments: The CHAT Study Group is Melissa Mc- Carthy, ScD, Ellen MacKenzie, PhD, Dennis Durbin, MD, MS, Charles Paidas, MD, Mary Aitken, MD, MPH, Kenneth M. 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