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Approval for this study was granted by the Upper South New Zealand Regional Ethics Committee, and written informed consent was obtained from individuals who had experienced a TBI and from an orthopedic comparison group. The data reported here are part of a larger study examining the adult outcomes of childhood TBI. Participants were recruited via an audit of the neurosurgeon’s historical files, an audit of Hospital Emergency Department and Admission Records, and by placing notices in the community. General inclusion criteria for the study were that each participant had experienced an injury event as a child aged 0-17 years, were now 18 years or older, and more than 5 years post injury. Inclusion criteria for the moderate/severe TBI group included the following: i) clinical diagnosis of moderate or severe TBI; ii) skull fracture, evidence of lesion on tomography; iii) cerebral haemorrhage or Post-Traumatic Amnesia (PTA) > 24 hrs. Participants were included in the mild TBI group if they met the following criteria: i) a clinical diagnosis of mTBI; ii) loss of consciousness (LOC) < 20 min; iii) Post-Traumatic Amnesia (PTA) < 1 h; iv) no evidence of skull fracture or lesion on tomography. Participants in the orthopaedic injury control group were included if they had fractured an arm or leg in childhood and were excluded if they had ever experienced a TBI event. Recruitment yielded three groups of participants: 62 individuals with moderate/severe childhood TBI (21 female) aged 18-30 years (M = 23.29, SD = 3.55); 62 individuals with mild childhood TBI (29 female) were aged 18-30 years (M = 22.31, SD = 2.78), and the 43 orthopaedic controls (24 female) were aged 18-27 years (M = 21.81, SD = 3.36). All participants were fluent in English. Each participant was asked to attend a 3 hour test session conducted at the University of Canterbury. At the conclusion of the testing session, each participant was asked to nominate a family member, where possible, to complete the questionnaires described below. Family members (Mod/severe TBI=54; Mild TBI=51; Control=36) were sent the questionnaires to complete and return (Mod/severe=26/54, 48.1%; Mild TBI=20/51, 39.2%; Control=14/43, 32.6%). Analyses presented here were conducted on this sub-sample of participants.
Demographic characteristics including sex and age were collected using a structured interview. Information regarding injury severity was collected using a file review. Pre-morbid IQ (PVIQ) was estimated using the National Adult Reading Test (NART) [26-30]. An executive function domain score was estimated from the mean standardized scores of the following tests; the verbal fluency subtest of Delis Kaplan Executive Functioning System [31] which requires each participant to generate as many different words as they can in 60-seconds that begin with the letters F,A and S; the Colour-Word interference – inhibition subtest of the D-KEFS in which the participant is presented with a page containing the words “red,” “green,” and “blue” printed incongruently in red, green, or blue ink, and asked to say the colour of the ink in which each word is printed as quickly as possible without making mistakes; The Matrix Reasoning subtest of the Wechsler Abbreviated Scale of Intelligence [32], where each participant selects among five alternatives the correct item needed to complete a presented sequence of geometric figures and patterns; The copy phase of the Rey-Osterreith Complex Figure Test [33] was used to determine an organizational planning score based on Organizational Scoring System for Amnesiacs [34] (Kixmiller et al. 2000), which measures planning by scoring the way in which the replication was ordered and organized; and a Tower of London task presented and completed on a touch screen computer provided a measure of executive planning by measuring ability to transform the start state into the goal state by moving coloured balls across three graduated rods. A working memory/attention score was also estimated using the standardized scores of the Adaptive Digit Ordering Task [35] (DOT-A: Werheid et al., 2002), which provides a measure of verbal working memory and requires the participant to recall an increasing sequence of numbers in ascending order; and the Daneman and Carpenter Reading Span test [36] (DCRS: Daneman & Carpenter, 1980) where each participant is required to read aloud sentences consisting of eight to thirteen words, judge whether the sentence makes sense or not, and recall the last word in each of the sentences. The FrSBe [25] was used to quantify behaviours associated with frontal lobe brain damage. It has demonstrated validity in the assessment of behavioural dysfunction and disturbances associated with frontal-subcortical circuitry damage and TBI. The total score consists of three sub-scales: apathy, disinhibition, and executive Dysfunction. The self-rated version consists of 46 items rated on a 5-point Likert scale that measure behaviour before illness or injury and at the present time. All scores were converted to T-scores corrected for age, education, and gender according to the FrSBe administration manual [25], T-scores < 60 are considered normal; scores of 60-64 are considered of borderline significance, and scores of 65 or above are considered clinically significant. Clinically significant scores on the apathy subscale suggest problems with initiation, psychomotor retardation, spontaneity, drive, persistence, loss of energy and interest, lack of concern about self-care, and/or blunted affective expression. Clinically significant scores on the disinhibition subscale suggest difficulties with inhibitory control, impulsivity, hyperactivity, social inappropriateness or lack of conformity to social convention, excessive emotional expression, emotional lability, explosiveness, and/or irritability. Clinically significant scores on the executive dysfunction subscale denote self-reported problems with sustained attention, working memory, organization, planning, future orientation, sequencing, problem solving, insight, mental flexibility, self-monitoring of on-going behaviour, and/or ability to benefit from feedback or modify behaviour following errors [25]. The current study measured the behaviours at the present time only as participants were injured during childhood and adolescence.
Data are presented as mean ± SD. Differences between groups in demographic characteristics and behavioural measures were assessed using analysis of variance (ANOVA). To control for the younger age at injury of the mild TBI group, age at injury as used as a covariate in all relevant analyses. Repeated measures ANOVA was used to explore differences between self and family scores between the groups. Bonferroni post-hoc tests were used to control for multiple comparisons. Pearson correlations were completed to determine the relationships between the self and family rated FrSBe scores, PVIQ, and the executive function and working memory/attention domain scores, with logistic regressions subsequently employed to assess the predictive utility of self or family FrSBe ratings on the domain scores. The agreement between the self and family FrSBe total score was measured using the Gower coefficient of agreement [37]. Briefly, the Gower index expresses the average absolute discrepancy between pairs of observations (scaled relative to the maximum possible discrepancy), which is then re-expressed as a measure of agreement by subtracting this discrepancy value from 1. It varies between 0 and +1, where +1 indicates identity between the two sets of observations. Computation of the Gower index was implemented using the 'Gower' computer program version 1.1 (www.pbarrett.net/software.html). The Gower coefficient of agreement has been used and validated in various disciplines including ecology, veterinary science, and cognitive science [38-40]. Because there is no obvious hypothetical sampling distribution for Gower coefficients, a bootstrap procedure was employed to compute credibility intervals (the interval within which we might expect to observe 95% of all coefficients computed using the same sample size, number-type (integers), and same minimum and maximum possible data range as that for the observed coefficient). A total of 10,000 resamples, of the same sample sizes used in the present study, from a uniform random number distribution were undertaken, from which the empirical sampling distribution of coefficients was created, and against which the observed coefficient could be assigned a probability of occurrence (the significance test) and an appropriate credibility interval constructed. Full details of the exact procedure are contained in the Bootstrap software used to perform the procedure (Bootstrap Version 1.0, http://www.pbarrett.net/Bootstrap/Bootstrap.html). All statistical calculations, except those pertaining to the Gower calculations, were made using SPSS 18 (IBM Corp., Somers, NY, USA).
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