Replication and Construct Validation of the BNI Screen for Higher Cerebral Functions with a Swedish Population*
Vera Denvall, MSc**
Sölve Elmståhl, MD, PhD**
George P. Prigatano, PhD
Division of Neurology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona
**Division of Geriatric Medicine, Department of Community Medicine, Lund University, Malmö, Sweden
*Reprinted with permission from the Journal of Rehabilitation Medicine, Taylor & Francis Group, Stockholm, Sweden.
A Swedish translation of the BNI Screen (BNIS) for Higher Cerebral Functions was administered to 52 normal control subjects and 36 patients with well-documented brain dysfunction. Findings replicated those reported in American samples. Level of performance was strikingly similar between Swedish controls and American controls, especially in individuals between 15 and 39 years. Swedish patients with brain dysfunction performed at levels significantly below the Swedish control subjects. The sensitivity of the test was 83% (correctly classifying 30 of 36 patients); patients with a higher level of education were misclassified. The present study replicates earlier findings and adds to the construct validity of the BNIS, which also may prove useful for studying rehabilitation outcomes in Swedish patients.
Key Words: BNI Screen, higher cerebral function, neuropsychological screening, neuropsychology, neurorehabilitation
During past decades neuropsychological knowledge has increased dramatically, and neuropsychological assessment now plays an important role in the evaluation of brain dysfunctional patients.[1,17] Neuropsychological assessment may be conducted for many reasons: to aid in diagnosis, to provide potentially valuable information for rehabilitation management and care, to evaluate the efficacy of different rehabilitation methods, and to conduct research. A comprehensive neuropsychological investigation often requires several hours of testing.[8,9] Clinically, however, the time available to examine patients and the patients’ condition limit the length of neuropsychological investigations. Therefore, a short, standardized neuropsychological screening test with wide applicability could be quite useful clinically.
During the past 20 to 30 years, a number of screening tests have been developed, many to screen patients with possible dementia.[3,4,6,7,11,23] Typically, these screening tests do not provide clinicians with adequate information to establish a preliminary neurological diagnosis of focal, bilateral, diffuse, or lateralizing brain injury. Other screening tests have been developed to assess patients with traumatic brain injury, stroke, and various neurological conditions. [4,11,24] Many of these instruments, however, do not systematically assess patients’ emotional characteristics, which can be a valuable source of information for both the assessment process per se and the efficacy of rehabilitation. For example, the capacities to control impulses and to perceive and express affect are important for social interaction and whether these abilities are intact can influence the rehabilitation process.
The BNI Screen (BNIS) for Higher Cerebral Functions is a short screening test developed to systematically assess a variety of higher cerebral functions that would aid in differential diagnosis and treatment planning. The initial rationale for developing the BNIS was to provide examiners with both qualitative and quantitative information about cerebral dysfunction. An important component of this test is a prescreening measure that systematically helps an examiner to determine whether an individual has adequate cooperation, arousal, and language skills to be examined. Assuming that these basic functions are intact, the screen then permits the systematic assessment of speech and language functions, orientation, attention/concentration, visuospatial and visual problem-solving skills, memory, affect, expression, perception, and awareness. Sampling a wide range of behaviors, the BNIS has proven to be a rapid, reliable, and valid assessment of higher cerebral functions.[17,20]
The purpose of this study was to assess the construct validity of the BNIS in a Swedish population. If a Swedish translation of this test replicated the findings from American populations, it would establish the BNIS as a potentially helpful tool for assessing Swedish brain dysfunctional patients and for predicting rehabilitation outcomes as has been done with an American sample.[18,19] The present study compared the performance of healthy Swedish people with Swedish patients with brain injury and with data from American control subjects.
Materials and Methods
An invitation letter was sent to 519 citizens of Malmö between 30 and 90 years who were randomly recruited from the municipality registry. The response rate was 45%. Sixty-four subjects were then invited to a medical and neuropsychological examination after undergoing a preliminary interview by telephone. The aim was to recruit 50 healthy subjects, proportionally distributed between the ages of 30 to 89 years (by decade). The inclusion criteria were no brain dysfunction according to medical history, examination, or computed tomography (CT) of the brain; no psychiatric illness; no dyslexia; Swedish as their primary language; no color blindness; no serious vision or hearing problems; and no acute illness according to medical examination. All individuals older than 50 years were examined by CT of the brain to exclude subjects with pathological conditions. The subjects were recruited consecutively until the 10 age groups were filled. Of the 64 subjects examined, 12 were excluded: three each due to dyslexia, head trauma, and depression, two due to infarction revealed by the CT, and one due to migraine headaches. Ultimately, the control group was composed of 52 subjects (mean age, 56.6 years; age range, 30-87 years). There were 25 women (mean age, 58.8 ± 15.7 years) and 27 men (mean age, 54.4 ± 15.3 years, Table 1).
The patient group (n=36; mean age, 52 years; age range, 22-76 years) was recruited consecutively among brain dysfunctional patients who had undergone a neuropsychological examination. The patient group consisted of inpatients and members of a day-care unit who had come to the Department of Geriatric Medicine of Malmö University Hospital for a neuropsychological evaluation. There were 25 men (mean age, 54.4±15.6) and 11 women (mean age, 46.6±15). In all cases, brain injury was confirmed by CT or cerebral xenon blood flow studies. The patients’ diagnoses were classified according to the ICD-9 system (Table 2).
Chronicity (time since injury), level of education, and diagnoses were obtained from patients’ medical records and interviews with patients. All subjects who had passed the Swedish “gymnasium” were considered to have a “high” level of education and those who had not reached this level were considered to have a “low” level of education.
There were 200 American controls (144 females, 56 males, Table 1); their data are published elsewhere.
All subjects underwent a physical examination by a physician (data not reported). The neuropsychological investigation included the BNIS and was conducted by two psychologists at the clinic who were experienced in neuropsychological testing.
The BNIS consists of 30 different items grouped into seven clinically relevant factor scores with a maximum (Total) score of 50 (Table 3). The instrument takes 15 to 20 minutes to administer.
Group means were compared with a Mann-Whitney U-test if not otherwise stated. The Swedish and American samples were compared by t-tests. Spearman’s correlation coefficients were calculated to determine the relationship of age and education to BNIS scores. Proportional differences between groups were compared with a X test.
Swedish vs. American Controls
The mean BNIS Total score for the Swedish controls was 45.6±3.1,which is consistent with the mean for the American controls (45.5±3.6,Table 1).The BNIS Total score did not differ between males and females in either the Swedish controls (males, mean 46.1±3.1;females,mean 45.0±3.0) or the American controls (males, mean 45.8 ± 3.8; females, mean 45.4 ± 3.5). The proportions of males and females in the Swedish and American control groups differed significantly (p=0.002; Table 1). Education by years did not correlate significantly with test performance for the Swedish control group (r =0.2, p<0.016) but was significant for the American controls (r =0.31, p<0.001).
Age was a major influence on test performance for both the Swedish (r =–0 .59; p<0.0001) and American control (r =–0.55,p<0.0001) groups. Performance tended to decline as age increased. There were no significant differences in mean BNIS Total score between the Swedish and American control groups for three age ranges (15-39, 40-59, and 60-84 years, Table 4).
Swedish Patients vs. Swedish Controls
There were no differences between the Swedish patient and control groups in terms of age, sex, or education (Table 1).
The mean BNIS Total score of the patients with brain injury was lower than that of the controls (p<0.001). Chronicity (r =–0 .107) and age (r = 0.232) were not significantly related to performance but education was (r = 0.568, p<0.001). The mean BNIS Total scores of patients with “high” (n =17, mean BNIS score=42.5, standard deviation (SD)=5.77, range= 2.85–48) and “low” (n =18, mean BNIS score=38.1,SD=6.66, range=17.5–45) levels of education were significantly different (p<0.05;Table 5).
In addition to the BNIS Total score, the individual subscale scores were compared for patients and controls (Table 6). Performances on all subscales but awareness were significantly different between the two groups. On the awareness subscale, patients with brain injury were significantly more likely to overestimate (36%) their performance than controls who were more prone to predict correctly (63.5%) or to underestimate (19%) their test performance (p<0.05). On the awareness subscale, 90.2% of the American controls correctly predicted their performance compared with 63.5% of the Swedish controls.
The ability to predict performance on the memory task was also related to overall performance on the BNIS. Among individuals in the brain-injured group who underestimated or correctly predicted their performance on this scale, their mean BNIS Total score was 43.3 (SD=3.66, n =23) compared with 34.7 (SD=6.73,n=13, p<0.0001) for those who overestimated their mean score. In the control group, the mean BNIS Total score for those who underestimated or correctly predicted their memory performance was 46.1 (SD=3.02, n =43) compared with 43 (SD=2.18, n =9, p<0.01) for those who overestimated their performance.
Finally, the sensitivity, specificity, and false-positive and false-negative ratios were calculated at the recommended cut-off level on the BNIS Total score for detecting brain impairment. The sensitivity was 83% and the specificity was 46%. The false-positive ratio was 48%, and the false-negative ratio was 20% (i.e., 30 of the 36 patients were correctly classified as brain-injured). All those misclassified as not being brain injured had a “high” level of education.
The present study demonstrates that a Swedish translation of the BNIS is potentially a sensitive measure for detecting and measuring cerebral dysfunction among the Swedish population. The Swedish control group also performed at a level comparable to their American counterparts. In both the American and Swedish control groups, age and performance correlated significantly and at a comparable level (r=–0.55 and –0.59, respectively). The findings extend the construct validity of this instrument.
Educational levels significantly correlated with the performance of the American controls but did not reach statistical significance in the Swedish controls. However, education has been shown to influence the performance of cognitive testing. With a larger sample size, educational level may have influenced the performance of the Swedish controls.
The Swedish brain dysfunctional group clearly performed at a lower level on the BNIS than the Swedish controls. These data suggest that the BNIS discriminates Swedish brain dysfunctional patients from normal controls.
In both cultures, the role of education in influencing test performance was clearly seen in brain dysfunctional patients. This finding suggests that considering level of education when interpreting the BNIS Total score may be useful. Such a trend has been associated with other aspects of neuropsychological test interpretation. Ultimately, different “cut-off” scores, depending on the educational level of the individual to whom the test is being administered, may be needed. Presently, however, age-corrected T-scores are available, at least for the American population.
The individual subscale scores also distinguished patients from controls on all factors except awareness. In earlier studies by Prigatano et al. and Rosenstein et al., differences between brain-injured patients and controls were significant on the awareness item versus performance. In the Swedish sample, however, there was no difference on this factor. Brain-injured individuals tended to overestimate their performance, and the performance of the Swedish controls was consistent with earlier studies. The ability to estimate one’s performance correctly on recalling three words with distraction was related to the level of performance on the BNIS as reflected by the Total score in both patients with brain injury and controls. Thus, this variability also may need to be considered when findings are interpreted. Unlike the American population, Swedish controls tended to underestimate their abilities, a finding that may reflect a cultural difference.
The differences in mean individual factor scores between the brain-injured group and the controls on the three subscales language, visuospatial, and affect all reached the highest level of significance (p<0.0001,Table 6). Prigatano et al. discussed the importance of these three subscales in diagnosing right and left hemispheric lesions. Future studies will be designed to cross validate this finding.
In addition to its use as a diagnostic instrument, the BNIS has been used to predict the outcome of neurorehabilitation.[18,19] In a study of 106 patients with acute brain lesions, age-corrected Total scores on the BNIS at admission and discharge were higher for individuals who achieved their rehabilitation goals than for those who did not. Moreover, the amount of cognitive improvement, as measured by the BNIS, was related to more positive outcomes. Improvement in both cognitive and affective functioning, as measured by the BNIS, was related to rehabilitation outcome. Patients who ultimately achieved their rehabilitation goals more accurately predicted their memory performance (a possible measure of impaired awareness) and generally showed more spontaneous affect over the course of rehabilitation than those who did not.
Affective functions are often neglected by existing screening tests and more extensive neuropsychological test batteries. This tendency may have decreased the utility of neuropsychological tests for predicting rehabilitation outcomes. Prigatano and Wong have suggested that impatient neurorehabilitation of brain dysfunctional patients should foster not only improvement in cognitive functioning but should also help patients improve their spontaneous demonstration of affect, their capacity to perceive facial affect, and their capacity to generate affect in their tone of voice.
Whether the findings of Prigatano and Wong can be replicated in the Swedish population awaits to be demonstrated. The present findings, however, are encouraging insofar as they suggest that previously observed relationships between performance on the BNIS and brain dysfunction in American patients are similar to those in Swedish patients with brain injury. In particular, the performance of normal controls on the BNIS seems strikingly similar between Americans and Swedes.
The study was supported by the Swedish Board of Health and Welfare and the Kock Foundation.
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