Determining client cognitive status following mild ...

Scandinavian Journal of Occupational Therapy

ISSN: 1103-8128 (Print) 1651-2014 (Online) Journal homepage: http://www.tandfonline.com/loi/iocc20

Determining client cognitive status following mild traumatic brain injury Elizabeth Hobson, Natasha A. Lannin, Amelia Taylor, Michelle Farquhar, Jacqui Morarty & Carolyn Unsworth To cite this article: Elizabeth Hobson, Natasha A. Lannin, Amelia Taylor, Michelle Farquhar, Jacqui Morarty & Carolyn Unsworth (2015): Determining client cognitive status following mild traumatic brain injury, Scandinavian Journal of Occupational Therapy, DOI: 10.3109/11038128.2015.1082622 To link to this article: http://dx.doi.org/10.3109/11038128.2015.1082622

Published online: 12 Oct 2015.

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Date: 05 November 2015, At: 20:03

SCANDINAVIAN JOURNAL OF OCCUPATIONAL THERAPY 2015; EARLY ONLINE: 1–9 http://dx.doi.org/10.3109/11038128.2015.1082622

ORIGINAL ARTICLE

Determining client cognitive status following mild traumatic brain injury Elizabeth Hobson1,2, Natasha A. Lannin1,3, Amelia Taylor3, Michelle Farquhar3, Jacqui Morarty3 & Carolyn Unsworth1,4,5,6

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1 Department of Occupational Therapy, La Trobe University, Melbourne, Australia, 2Occupational Therapy Department, Royal Melbourne Hospital, Melbourne Health, Melbourne, Australia, 3Department of Occupational Therapy, The Alfred, Alfred Health, Melbourne, Australia, 4 Department of Occupational Therapy, Central Queensland University, Australia, 5School of Health Sciences, Department of Rehabilitation, Jo¨nko¨ping University, Sweden, and 6Department of Occupational Therapy and Social Work, Curtin University, Perth, Australia

ABSTRACT

KEYWORDS

Background: People with mild traumatic brain injury (mTBI) commonly experience cognitive impairments. Occupational therapists working in acute general hospitals in Australia routinely access client Glasgow Coma Scale (GCS) scores, and assess cognitive status using standardized tools and by observing basic activity of daily living (ADL) performance. However, limited evidence exists to identify the best assessment(s) to determine client cognitive status. Aim/objectives: To determine whether cognitive status assessed by GCS score and the Cognistat are predictive of basic ADL performance among clients with mTBI in an acute general hospital and make inferences concerning the clinical utility of these assessment tools. Material and methods: Retrospective analysis of medical record data on demographics, Cognistat, GCS, and modified Barthel Index (MBI) using descriptive statistics, chi-square tests and linear regression. Results: Data analysis of 166 participants demonstrated that no associations exist between GCS and Cognistat scores, or Cognistat scores and MBI dependency level. The presence of co-morbid multi-trauma injuries and length of stay were the only variables that significantly predicted MBI dependency level. Conclusion and significance: While the MBI scores are of value in identifying clients with difficulty in basic ADLs, Cognistat and GCS scores are of limited use in differentiating client levels of cognitive impairment and the authors caution against the routine administration of the Cognistat following mTBI. Further research is required to identify more suitable assessments for use with a mTBI population.

Activity of daily living, assessment, brain injuries, cognition, function, functional independence, occupational therapy

Introduction Mild traumatic brain injury (mTBI), as differentiated from a concussion syndrome, accounts for 70–90% of all hospital-treated traumatic brain injury (TBI) (1). People with mTBI frequently experience impairments in memory, attention, information-processing skills, and executive functions, typically resolving within one to three months post-injury (2–4). Although the degree of cognitive impairment is often mild, even subtle deficits can interfere with performance of activities of daily living (ADLs), and a direct relationship between mTBI and participation restrictions in work, community, and leisure activities has been well established (5,6). Occupational therapists play a valuable role in the assessment of cognition in people with mTBI (2,7,8), and therapists working in busy acute general hospitals are under pressure to quickly and accurately identify cognitive impairments, determine realistic goals, and

Correspondence: A/Prof Natasha Lannin, Tel: +613 94796745. Fax: +613 9533 2104. ! 2015 Taylor & Francis

HISTORY

Received 3 March 2015 Revised 13 July 2015 Accepted 10 August 2015 Published online 8 September 2015

identify the need for appropriate follow-up. The severity of cognitive impairments is often measured by the Glasgow Coma Scale (GCS) (9). While the use of the GCS to predict outcome has been criticised (10,11), many clinicians still rely on this scale as a primary indicator of TBI severity (12). However, its ability to accurately identify levels of cognitive impairment among clients with mild TBI has not been well researched. In addition to the GCS, a standardized cognitive screening tool is often administered by occupational therapists working in acute general hospitals. Internationally, a variety of assessments are used for this purpose including the Cognistat (known also as the Neurobehavioral Cognitive Status Examination) (13), Cognitive Performance Test (14), Executive Function Performance Test (15), and the Assessment of Motor and Process Skills (AMPS) (16). A benchmarking survey of Australian acute trauma service practices in mTBI

Department of Occupational Therapy, The Alfred, 55 Commercial Road, Melbourne, Victoria, 3004, Australia. [email protected]

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reported that the Cognistat (13) was the most commonly used cognitive screening tool by occupational therapists (17), and is also commonly used in New Zealand (18). The Cognistat is quick to administer and requires little training, making it useful in a busy acute general hospital. A criticism of ‘‘paper and pen’’ cognitive screening tools, such as the Cognistat, is that they are removed from everyday contexts and ineffective in predicting functional outcomes (19). Furthermore, while research conducted with stroke survivors has shown that the Cognistat’s comprehension and repetition subtests are useful in predicting independence in basic ADLs (20), research has not yet fully examined the relationships between Cognistat scores and ADL performance following mTBI. Occupational therapists routinely observe client ADL performance, and consider the impact of any cognitive impairments. While cognitive abilities have been shown to relate to functional independence for clients with stroke (20,21), research to date has not examined this relationship with people following mTBI. Occupational therapists routinely assess basic ADLs in areas including, bathing, dressing, grooming, feeding, toileting, and functional transfers using assessment such as the FIMTM (22) or a version of the Barthel Index (23). As mentioned earlier, although research has showed that impairments in work, community, and leisure occupations are common follow mTBI (5,6), it remains unknown whether subtle deficits of cognitive abilities influenced basic ADL performance. Determining the relationship between GCS, Cognistat, and basic ADL assessment scores would give therapists a better understanding of the importance of routinely administering both cognitive and basic ADL assessments following mTBI, assisting with resource allocation by providing support for, or refuting the continued use of these assessments. In summary, despite the label of ‘‘mild’’, impaired cognitive abilities following mTBI potentially interfere with basic and more complex ADLs (2,7). While the natural history of most cognitive impairment is that they resolve over a period of one to three months (3), early detection of deficits is imperative. This allows therapists to provide education to clients and families to minimize the effects of impairments, introduce interventions to promote recovery, and support return to pre-injury functioning (24). In the hospital where this study was conducted, GCS scores were available for all people with mTBI, and for several years the occupational therapists have routinely collected Cognistat and MBI scores for all clients. However, it was not clear what the relationships were between scores on the assessments and, indeed, whether the

Cognistat and GCS scores were able to discriminate levels of severity of cognitive impairment among mTBI clients. Therefore, the purpose of the present study was to determine if the assessments currently administered at the acute general hospital where the study was conducted are the best to use, or if new assessments should be considered in the future. Specifically the aims were to: (1) examine the ability of the Cognistat and GCS to differentiate between clients with differing levels of cognitive status; (2) examine the ability of the MBI to differentiate clients with differing levels of basic ADL dependency; and (3) examine the relationships between client demographic variables, Cognistat and MBI scores. These aims would enable a greater understanding of the quality of information gathered on these assessments and the value of these scores in identifying mTBI clients with problems needing further evaluation and intervention. It was reasoned that this research would provide important information to support the continued use of these assessments, or highlight the need for new assessment tool(s).

Materials and methods Participants The medical records of eligible participants were reviewed. Eligible participants were adults aged 18 years and over with mTBI who had entered through the emergency unit, been admitted to the trauma unit and referred to Occupational Therapy Services, between July 2012 and January 2013. The hospital is one of the largest in Australia, admits over 5000 patients annually to the trauma unit, and services a city with a population of 4.5 million inhabitants. Eligible participants had sustained a recent trauma to the head with at least one of the following indicators: new traumatic changes on the initial computerized tomography brain scan, a period of loss of consciousness (LOC) not exceeding 30 minutes, a period of post-traumatic amnesia (PTA) not exceeding 24 hours, and/or 30 minutes post-injury a GCS score of 13 to 14 (25). In accordance with the operational definition of mTBI defined by the American Congress, we excluded those participants suffering a concussion syndrome (26). Participants with a history of chronic substance abuse, a psychotic disorder, previous brain injury, dementia, or intellectual disability were excluded to avoid possible confounding effects of premorbid cognitive impairments (26). We also excluded people who did not speak fluent English or who were

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93 years or older, in accordance with available Cognistat norms (27). Instruments

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Glasgow Coma Scale The GCS was used to identify depth of impaired consciousness following the mTBI (9). Three domains are assessed: eye opening (scored from 1 to 4), best verbal response (scored from 1 to 5), and best motor response (scored from 1 to 6), with higher scores indicating less impairment. Although there is a large body of literature around the GCS, there is relatively limited information available on its psychometric properties (28). However, studies have demonstrated construct validity for the three severity bands (severe less than 9, moderate 9 to 12, and minor 13 or greater), inter-rater reliability of r ¼ 0.95, and test–retest reliability of 0.85 (28). Cognistat Cognition was assessed using the Cognistat, a standardized screening tool with 10 subtests: orientation, attention, language (comprehension, repetition, and naming), constructional abilities, memory, calculations, and reasoning (similarities and judgements) (13). The assessment takes five to 20 minutes to administer. For each subtest a score is calculated according to established criteria and this score is presented on a performance ability profile: average, mild impairment, moderate impairment, severe impairment (14). Since the Cognistat does not purport to discriminate average from superior performance, authors suggested usual reliability criteria would yield high scores of little relevance (13). Prior studies have calculated adequate internal consistency reliability (Cronbach’s alpha ¼ 0.75) (29) when administered to adults with brain injury, adequate to excellent convergent validity with corresponding items from other screening tools in a mixed brain injury and stroke population (Pearson’s ranged from r ¼ 0.53 to 1.0, p50.05) (29), and adequate to excellent concurrent validity with neuropsychological tests in a brain-injured population (Pearson’s ranged from r ¼ 0.30 to 0.83, p50.05) (30). Mithrushina, Abara and Blumenfeld subjected the scores of psychiatric patients on the 10 subscales to factor analysis. Two factors were extracted accounting for 50% of the common variance; factor 1 comprised overlearning skills based on education and experience, and factor 2 – primarily defined by Memory, Judgment and Calculations – represented abilities associated with functional efficiency with regard to the immediate

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environment (31). In this study, we applied the normative data from research of the highest methodological quality for each age group. As a result, we extended the range of performance designated as average for the geriatric population in these subtests. Using the proposal from Macaulay et al. (32), the range of performance designated as average differed for those aged 65 to 74 years in the Memory subtest, 75 to 84 years in the Memory and Constructional Abilities subtests, and 85 to 92 years in the Memory, Constructional Abilities, and Similarities subtests. Modified Barthel index Independence in basic ADLs was assessed using the MBI (23). The assessment has 10 items: feeding, personal grooming, toileting, bladder control, bowel control, bathing, dressing, ambulating or wheelchair operation, chair/bed transfers, and stair climbing (23). These 10 ADLs are each rated with five levels of dependency (from 1, or unable to perform task, to 5, or fully independent); the maximum score is 100 points, representing independence in daily living. Total scores are then able to be categorized into dependency levels: 0 to 20 total dependency, 21 to 60 severe dependency, 61 to 90 moderate dependency, 91 to 99 slight dependency, and 100 independent. Assessors scored the assessment based on direct observation, discussion with the client, family, or another clinician, or using information obtained from medical records (23). The MBI has excellent internal consistency, suggestive of acceptable factor structure within the 10 items (Cronbach’s alpha ¼ 0.90) in a stroke population (23), and the inter-rater reliability was moderate to good at the item level (kappa (), ranging from 0.52 to 0.88) and excellent overall (intra-class correlation coefficient ICC ¼ 0.98) in a mixed orthopaedic and neurological population (33). Moreover, the MBI has demonstrated predictive validity following TBI (34) and excellent convergent validity with other measures of ADL performance (Pearson’s ranged from r ¼ 0.86 to 0.96, p50.05) (24). Procedure The study was approved by La Trobe University and Alfred Health Research Ethics Committees. The need to gain participant consent was waived as the data had previously been collected using routinely administered assessments. All data were de-identified. The medical records of consecutively admitted people diagnosed with mTBI were screened for inclusion. Study investigators gathered demographic and injury-related data, Cognistat scores, MBI scores, and GCS information from

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participants’ medical records. GCS scores had all been recorded by paramedic, nursing, or medical staff 30 minutes post-injury and were gathered from the ambulance or emergency unit reports. The Cognistat was performed by the treating occupational therapist trained in administration and scoring of the tool as per the test manual (13). Clients were not assessed until they were considered to have emerged from PTA and had ceased opiate-based pain relief. Within two days of having the Cognistat administered, the treating occupational therapist scored the MBI as per the standardized instructions (24).

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Data analysis Data were analysed using the Statistical Package for Social Sciences VersionTM 21.0 (IBM Corp, Armonk, NY, USA). Descriptive statistics were used to summarize demographic data. Glasgow Coma Scale scores were recoded into mild GCS subgroup (score ¼ 14 and 15) and a moderate–mild GCS subgroup (score ¼ 13) for further analysis. The coding of GCS scores was based on evidence suggesting individuals with a GCS score of 13 have a more severe presentation of injury than those with a GCS score of 14 or 15 (35). To fulfil the second aim, chi-square tests were used to examine the associations between performance on each Cognistat subtest, and MBI dependency level and the two GCS subgroups, respectively. Statistical significance was set at p50.05. Spearman’s rho, rs, (two-tailed) was used to measure the strength of statistically significant associations. Nonparametric tests were chosen since several variables were not normally distributed (36). To fulfil the third aim, linear regression was used to examine the ability of Cognistat subtest results and selected demographic and injury-related variables to predict MBI dependency level, providing assumptions of regression were not violated (37). Variables significantly associated with MBI dependency level as tested using chi-square were entered into the model as independent variables, as were Cognistat subtests (with sample sizes greater than six clients with impaired performance), and age, since literature relates age to functional independence in basic ADLs following mTBI (38). This was done with the intent of ensuring the model controlled for the contribution of these factors to other variables, and was consistent with reported literature. Regression coefficients and their associated standard errors were reported. In addition, the relevant probabilities for testing that the regression coefficient was statistically different from zero (no effect) were also reported. Criteria for interpreting the value of the coefficient of determination were based on the guidelines specified by Cohen (39).

Results Client demographic data and test scores A total of 248 medical records of people diagnosed with mTBI during the study period were screened. Eighty-two participants were excluded due to: chronic substance abuse (n ¼ 45), non-fluent English language ability (n ¼ 18), previous brain injury (n ¼ 9), psychotic disorder (n ¼ 8), intellectual disability (n ¼ 3), and dementia (n ¼ 1) noting that criteria were not mutually exclusive. The final sample included 166 participants with ages ranging from 16 to 92 years (mean ¼ 41, SD 19). Demographic and injury-related characteristics are provided in Table I. As indicated in Table I, the vast majority of participants scored 14 or 15 on the GCS. The Cognistat was administered an average of two days postadmission (SD ¼ 3). Raw frequencies and percentages by performance ability profiles for each Cognistat subtest are reported in Table II.

Table I. Participant characteristics (n ¼ 166). Characteristic Age in years (mean, SD) 41 (19) Length of acute stay in days (median, IQR) 3 (2,6) Gender (n, %) Male 122 (74) Highest level of education achieved (n, %) Less than secondary school 45 (27) Secondary school or equivalent 14 (9) Technical college 19 (11) University qualification 20 (12) Not recorded 68 (41) Employment/vocational status (n, %) Full time 91 (55) Part time 19 (12) Student 14 (8) Other (home duties, unpaid carer, unemployed, 41 (24) receiving benefits) Not recorded 1 (1) Marital status (n, %) Single 62 (37) Married/partner 93 (56) Widow/widower 6 (4) Divorced/separated 4 (2) Not recorded 1 (1) Mechanism of injury (n, %) Road traffic accident 86 (52) Mechanical fall 29 (17) Sporting/recreational accident 26 (16) Assault 13 (8) Occupational accident 7 (4) Other 5 (3) Known LOC (n, %) 101 (61) Known period of PTA (n, %) 66 (40) New traumatic abnormalities as detected by CT brain scan (n, %) 61 (37) GCS score 30 minutes post-injury (n, %) 13 17 (10) 14 or 15 121 (79) Not recorded 18 (11) Co-morbid multi trauma injuries sustained (n, %) None 81 (49) Notes: SD ¼ standard deviation; LOC ¼ loss of consciousness; PTA ¼ posttraumatic amnesia, CT ¼ computerized tomography; GCS ¼ Glasgow coma scale; ADL ¼ activities of daily living.

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Table II. Descriptive data for the Cognistat. Subtest

n

Orientation Attention Comprehension Repetition Naming Constructional ability Memory Calculations Similarities Judgement

Performance ability profile

166 166 162 166 166 119 165 163 165 165

Average performance n (%)

Mild impairment n (%)

Moderate impairment n (%)

Severe impairment n (%)

160 151 161 148 165 111 113 142 154 163

6 10 1 15 1 4 26 17 6 0

0 5 0 3 0 3 11 4 3 2

0 0 0 0 0 1 15 0 2 0

(96) (91) (99) (89) (99) (93) (68) (87) (93) (99)

(4) (6) (1) (9) (1) (3) (16) (10) (4) (0)

(0) (3) (0) (2) (0) (3) (7) (2) (2) (1)

(0) (0) (0) (0) (0) (1) (9) (0) (1) (0)

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Notes: n ¼ number of participants who completed the subtest.

Table III. GCS subgroups and Cognistat subtest performance ability profile. Subgroup

Cognistat subtest performance ability profile Orientation Attention Comprehension Repetition Naming n (%) n (%) n (%) n (%) n (%)

Construction Memory Calculations Similarities Judgement n (%) n (%) n (%) n (%) n (%)

Mild (GCS score ¼ 14 or 15) 125 (95) 6 (5)

124 (95) 5 (4) 2 (1)

128 (99) 1 (1)

122 (93)* 7 (5)* 2 (2)

131 (100) 91 (96) 2 (2)* 2 (2)

Moderate-mild (GCS score ¼ 13)

15 (88) 1 (6) 1 (6)

15 (100)

13 (76)* 4 (24)*

17 (100)

17 (100)

9 (82) 2 (18)*

92 (71) 20 (15) 9 (7) 9 (7)* 12 (71) 1 (6) 4 (23)*

117 (91)* 10 (8) 1 (1)*

125 (96) 4 (3) 1 (1)

129 (99) 1 (1)

12 (71) 3 (18) 2 (11)*

16 (94) 1 (6)

17 (100)

Notes: Comparisons of categorical proportions are statistically significant based on two-sided tests with significance level of 0.05. Cognistat subtest performance ability profile: regular type ¼ average range; italic type ¼ mild impairment; bold type ¼ moderate impairment; bold italic type ¼ severe impairment. GCS ¼ Glasgow Coma Scale.

On average, the MBI was scored within one day of administering the Cognistat (range 0–2). Some 28% (n ¼ 47) of participants were rated as independent, 15% (n ¼ 26) as slightly dependent, 31% (n ¼ 51) as moderately dependent, 19% (n ¼ 31) as severely dependent and 7% (n ¼ 11) as totally dependent. Ability of assessments (Cognistat, GCS, and MBI) to differentiate clients The first and second aims of this study were to examine the ability of the Cognistat and GCS to differentiate between clients with differing levels of cognitive status, and the MBI to differentiate between clients with differing levels of basic ADL dependency. The distribution of scores for the Cognistat in Table II show that the majority of clients, for each subtest, scored within the average range of performance. Frequencies of performance ability profiles in each Cognistat subtest for each GCS subgroup are presented in Table III; statistical comparisons of categorical proportions were tested using chi-square tests. Associations between GCS subgroups and Cognistat test performance were statistically significant in the following subtests: Repetition (2(2) ¼ 7.41, p ¼ 0.025, rs ¼ –0.18, p ¼ 0.026), Constructional Abilities

(2(2) ¼ 7.19, p ¼ 0.027), Calculations (2(2) ¼ 11.10, p ¼ 0.004, rs ¼ –0.22, p ¼ 0.007), and Similarities (2(3) ¼ 8.31, p ¼ 0.040). In other words, membership in the moderate–mild GCS subgroup (score ¼ 13) was associated with a poorer performance ability profile in these subtests. However, examination of the strength of statistically significant associations revealed that little or no relationship existed between variables. Comparison of categorical proportions showed that GCS subgroup influenced Cognistat performance ability profile on certain subtests. For example, a mild impairment on Constructional Abilities was more associated with membership in the moderate–mild GCS subgroup (score ¼ 13), than the mild GCS subgroup (score ¼ 14 to 15). No statistically significant associations were evident between GCS subgroups and Cognistat performance ability profiles in: Orientation, Attention, Comprehension, Naming, Memory, and Judgement subtests (p40.05). Frequencies of performance ability profiles on Cognistat subtests for each MBI dependency level are presented in Table IV. The distribution of scores across dependency levels indicated the MBI was able to differentiate between participants with basic ADL impairments. Statistical comparisons of category proportions for

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Table IV. Cognistat subtest performance ability profile and modified Barthel index dependency level.

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Dependency level

Cognistat Subtest Performance Ability Profile ORI n (%)

ATT n (%)

COMP n (%)

REP n (%)

NAM n (%)

CONST n (%)

MEM n (%)

CALC n (%)

SIM n (%)

JUD n (%)

Independent

47 (100)

46 (98) 1 (2)

47 (100)

45 (96) 2 (4)

47 (100)

37 (97) 1 (3)

40 (87) 4 (9) 2 (4)

46 (98) 1 (2)

47 (100)

Slight

25 (96) 1 (4)

25 (96) 1 (4)

25 (96) 1 (4)

23 (89) 2 (7) 1 (4)

26 (100)

17 (89)* 2 (11)*

23 (92) 1 (4) 1 (4)

25 (96) 1 (4)

26 (100)

Moderate

47 (92) 4(8)

45 (88) 4 (8) 2 (4)

50 (100)

44 (87) 6 (12) 1 (2)

50 (98) 1 (2)

35 (92) 2 (5) 1 (3)

41 (82)* 9 (18)*

31 (100)

25 (81)* 5 (16)* 1 (3)

30 (100)

28 (90) 2 (7) 1 (3)

31 (100)

17 (90) 1 (5) 1 (5)

27 (87) 3 (10) 1 (3)

44 (88) 3 (6) 1 (2) 2 (4) 28 (90) 2 (7) 1 (3)

49 (96) 1 (4)

Severe

Total

10 (91) 1 (9)

10 (91) 1 (9)

9 (100)

8 (73)* 3 (27)*

11 (100)

5 (100)

34 (74) 7 (15) 3 (7) 2 (4) 22 (84) 1 (4) 1 (4) 2 (8) 31 (60) 10 (20) 3 (6) 7 (14) 17 (55) 6 (19) 4 (13) 4 (13) 9 (82) 2 (18)

11 (100)

11 (100)

10 (91)* 1 (9)*

31 (100)

Notes: Comparisons of categorical proportions are statistically significant based on two-sided tests with significance level of 0.05. Cognistat subtest performance ability profile: regular type ¼ average range; italic type ¼ mild impairment; bold type ¼ moderate impairment; bold italic type ¼ severe impairment. ORI ¼ Orientation; ATT ¼ Attention; COMP ¼ Comprehension; REP ¼ Repetition; NAM ¼ Naming; CONST ¼ Constructional Abilities; MEM ¼ Memory; CALC ¼ Calculations; SIM ¼ Similarities; JUD ¼ Judgement.

Cognistat and MBI were tested using chi-square tests. No statistically significant associations were evident between MBI dependency levels and performance in any Cognistat subtest: Orientation (2(4) ¼ 6.49, p ¼ 0.165), Attention (2(8) ¼ 11.49, p ¼ 0.175), Comprehension (2(4) ¼ 5.26, p ¼ 0.261), Repetition (2(8) ¼ 8.55, p ¼ 0.381), Naming (2(4) ¼ 2.27, p ¼ 0.686), Constructional Abilities (2(12) ¼ 11.21, p ¼ 0.511), Memory (2(12) ¼ 12.67, p ¼ 0.339), Calculations (2(8) ¼ 7.95, p ¼ 0.438), Similarities (2(12) ¼ 10.03, p ¼ 0.613), and Judgment (2(4) ¼ 7.24, p ¼ 0.124). However, comparisons of categorical proportions showed some MBI dependency levels were related to Cognistat performance ability profiles. For example, being rated as severely dependent on the MBI was more associated with mildly impaired, than average performance in the Attention subtest of the Cognistat. Given the absence of any statistically significant associations, participants with a co-morbid multitrauma injury (which could have affected independence in basic ADLs) were excluded from the analysis. Again no statistically significant associations were evident between MBI dependency level and performance in any Cognistat subtest (p40.05). Relationships between client demographic variables, Cognistat, and MBI scores In relation to the third aim of the study, an inspection of graphed data for the Cognistat and MBI was conducted and it was determined that the assumptions for linear

regression were met. Presence of co-morbid multitrauma injuries (2(4) ¼ 48.94, p50.0001) and length of stay (rs ¼ .65, p50.0001) demonstrated significant associations with MBI dependency level. Six of the Cognistat subtests showed greater than six cases of impaired performance (see Table II). The results of the regression indicated that sustaining co-morbid multitrauma injuries (regression coefficient ( ) ¼ 0.948; standard error ¼ 0.189; 95% confidence interval (CI) ¼ 0.573–1.323) and length of acute stay ( ¼ 0.002, standard error ¼ 0.005; 95% CI ¼ 0.058–0.137) were the only independent variables in the model that exceed the conventional benchmarks for statistical significance. All other variables fell considerably short of that benchmark. Sustaining a co-morbid multi-trauma injury and length of acute stay also explained a significant proportion of variance in MBI dependency level, R2 ¼ 0.428, F(8,110) ¼ 4.927, p ¼ 0.000. Consistent findings were noted when the MBI total score was used as the dependent variable in the regression model. Regression coefficients for each statistically significant variable measure the contribution that the variable makes to the model. Thus, sustaining a co-morbid multi-trauma injury predicted a drop in one MBI dependency level (for example, from slight dependency to fully independent) and an increase in length of stay by one day predicted a drop in 0.002 of an MBI dependency level. While statistically significant, the latter contribution did not reach clinical significance; 500 days spent in hospital would be required to predict a drop by one MBI dependency level.

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Discussion Data analyses revealed no relationship between Cognistat test performance and independence in basic ADLs in people with mTBI. The majority of participants scored within the average range of performance on all Cognistat subtests, and GCS scores (within the range of 13 to 15) were not associated with cognitive status as measured by the Cognistat. Meta-analytic reviews have revealed that when persons with mTBI were assessed using sensitive, valid, neuropsychological tests most showed acute cognitive impairments (2–4). However, what this current research has shown is that the Cognistat cannot discriminate average from impaired cognition in cases of mild TBI. This finding is supported by other research in which a large proportion of a high-functioning TBI population scored disproportionally high on the Cognistat (40). Similarly, a more recent study using Rasch analysis found domains of the Cognistat could not differentiate between community-dwelling individuals with TBI who scored within the average range of performance from those who did not (41). The MBI appropriately differentiated between individuals with basic ADL limitations. Yet findings did not support a relationship between Cognistat test performance and independence in basic ADLs as measured by the MBI. The lack of relationship was surprising, as many basic ADLs require the underlying cognitive skills that the Cognistat purports to assess. In addition, these findings are in contrast to others that showed certain Cognistat subtests are useful in predicting functional independence in basic ADLs in other neurological populations (20). The absence of associations in the present study may be explained by the under-detection of cognitive impairments on the Cognistat. For a significant association to be found on chi-square testing, an individual’s cognitive impairment must affect his/her orientation, attention, language, construction, memory, calculation, or reasoning skills, as well as his/her ability to undertake basic ADLs. To ensure our findings were not skewed by the high proportion of the sample with co-morbid multi-trauma injuries, which were most commonly orthopaedic in nature, we excluded these participants and re-examined the data. Again, MBI scores were distributed across the five dependency levels but no statistically significant associations between Cognistat test performance and MBI dependency level were found. This demonstrated that participant co-morbid multi-trauma injuries did not account for the varied basic ADL performance in our sample, and did not confound our study findings.

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Sustaining a co-morbid multi-trauma injury was the only factor significantly related to MBI dependency level. Intuitively, it would be expected that the presence of injuries that often result in limb weightbearing restrictions would be associated with dependency in basic ADLs. However, this factor had not previously been identified as a variable related to independence in basic ADLs following mTBI. Age was cited in the literature as related to basic ADL performance after mTBI (38), but its contribution was not statistically significant in this study. At the participating hospital, occupational therapists use clinical reasoning to determine the appropriateness of administering the Cognistat to each mTBI client aged 65 years and above. Anecdotal feedback from these therapists suggested the group of elderly clients assessed using the Cognistat represents a higher functioning sample of this population, likely accounting for our differing findings. Two subgroups of mTBI clients were defined according to GCS scores: a mild subgroup (score ¼ 14 or 15) and a moderate-mild subgroup (score ¼ 13). When these subgroups were compared and their performance on Cognistat subtests purporting to assess domains of cognitive functioning known to be impaired following mTBI were tested, we found no significant associations. Our results suggested that GCS scores cannot be used to identify which clients require further cognitive assessment following mTBI. This finding was in accordance with previous research examining the relationship between GCS scores and cognition following mTBI (42,43). However, the under-detection of cognitive impairment on the Cognistat needs to be carefully considered, before making the conclusion that homogeneity exists with respect to cognitive status in all clients with a GCS score of 13 to 15. Across both GCS subgroups, a large proportion of participants scored quite high on the Cognistat. While it is tempting to conclude that GCS scores are not related to cognitive status, it remains unlikely that homogeneity exists with regard to cognitive functioning in all people with an mTBI and a GCS score of 13 to 15. In fact, our findings revealed partial support for the notion of heterogeneity within this group. Those with a GCS score of 13 (moderate–mild subgroup) did differ from those with a score of 14 or 15 (mild subgroup) in a limited number of cognitive domains. Therefore, the lack of relationship found overall between GCS subgroups and Cognistat test performance highlights the need to use other more sensitive assessments when investigating cognitive impairment in the context of mTBI.

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Limitations, implications for practice, and directions for further study The findings of this study are limited to clients with mTBI. In addition, while the strict exclusion criteria applied in this study reduced the effects of confounding variables, this also may limit the generalizability of findings to the broader mTBI population (26). The findings generate several implications for the occupational therapy management of people with mTBI during an acute general hospital admission. First, it appears that the Cognistat may not be sensitive enough to detect cognitive impairment in people with mTBI and therefore should be used with caution to inform decisions regarding discharge planning and ongoing rehabilitation needs. Further research is warranted to investigate the use of other assessments such as the AMPS (16) for this purpose. Second, an assessment of basic ADL performance should be routinely administered in all clients with mTBI as impairments exist in even those without comorbid multi-trauma injuries. Although the MBI was used in this study, it would appear that other assessments such as FIMTM (22) could be routinely used. Finally and importantly, it appears that the GCS scores recorded 30 minutes post-injury should not be used to distinguish between levels of cognitive impairment within the range of GCS 13 to 15 for people following mild TBI.

Conclusion This study questions the current practice of using the GCS and Cognistat to determine level of cognitive impairment for people with acute mTBI. Building on previous research which also revealed that the Cognistat was not a suitable assessment to use in high-functioning TBI populations, we caution against the routine administration of the Cognistat in people diagnosed with mTBI. Our findings highlight the need for future research to determine a more suitable assessment to identify clients who have cognitive impairment that may warrant further occupational therapy intervention. Further, we attributed the absence of relationships found between level of cognitive impairment and performance in basic ADL to the under-detection of cognitive impairments on the Cognistat. It is anticipated that use of a more suitable cognitive assessment tool in future research will be able to confirm the relationship between cognitive abilities and basic ADL performance.

Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

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