OBJECTIVE: Dispersion is a form of intra-individual variability across neuropsychological tests that has been shown to predict cognitive decline. However, few studies have investigated the stability and predictive utility of both across- and within-domain dispersion. The current study aims to fill these gaps in the literature by examining multiple indices of dispersion in a longitudinal clinical sample of individuals diagnosed with mild cognitive impairment (MCI) at baseline.
METHODS: Two hundred thirty-eight MCI patients from a cognitive disorders clinic underwent testing at baseline and after approximately 1.5 years. Linear regression was used to examine whether baseline across- and within-domain dispersion predicted cognitive decline in individuals whose diagnostic classification progressed to dementia (i.e., MCI-Decline) and those who retained an MCI diagnosis at follow-up (i.e., MCI-Stable). Cognitive decline was operationalized dichotomously using group status and continuously using standardized regression-based (SRB) z-scores.
RESULTS: Dispersion variables at baseline and follow-up were positively correlated in both groups, with the exception of within-domain executive functioning and language dispersion in the MCI-Decline group. None of the dispersion variables predicted diagnostic conversion to MCI. Using SRB z-scores, greater across-domain dispersion predicted greater overall cognitive decline at follow-up, but this was not the case for within-domain variables with the exception of visuospatial skills.
CONCLUSIONS: Results suggest that across- and within-domain dispersion are relatively stable across time, and that across-domain dispersion is predictive of subtle cognitive decline in patients with MCI. However, these results also highlight that findings may differ based on the tests included in dispersion calculations.

OBJECTIVE: Concussion is a growing public health concern given the large number of youth and collegiate athletes participating in collision sports. Sport-related concussions can have an adverse impact on student-athletes\' health and academic performance. Athletic programs within academic organizations are motivated to employ the most effective and efficient diagnostic and recovery procedures to minimize the duration and impact of these symptoms on student-athletes\' functioning. The present study sought to further our understanding regarding the value and frequency of conducting baseline assessments when evaluating sport-related concussions.
METHODS: A total of 41 athletes (24 men, 17 women) between the ages of 18 and 22 were evaluated following suspected concussive injury between 2015 and 2018. Post-injury test results were compared to baselines that had been collected either 1 or 2 years prior, and to normative data, to determine consistency in diagnostic outcomes.
RESULTS: Baseline test/retest reliability using Pearson\'s bivariate correlations revealed modest correlations on measures of verbal and visual memory (0.437-0.569) and very strong correlations on measures of reaction time and visual-motor speed (0.811-0.821). Meanwhile, minimal if any differences in clinical decision-making regarding the diagnostic outcome was observed when comparing post-injury test results to different baselines and to normative data.
CONCLUSIONS: Findings indicate that yearly baseline testing may not improve diagnostic accuracy, and in many cases, normative data may be adequate for decision-making. Additional research should evaluate the potential benefit of baseline testing in return-to-play decision-making among broader athletic populations.

The Cambridge Neuropsychological Test Automated Battery (CANTAB) is a battery of computerized neuropsychological tests commonly used in Europe in neurology and psychiatry studies, including clinical trials. The purpose of this study was to investigate test-retest reliability and to develop reliable change indices and regression-based change formulas for using the CANTAB in research and practice involving repeated measurement. A sample of 75 healthy adults completed nine CANTAB tests, assessing three domains (i.e., visual learning and memory, executive function, and visual attention) twice over a 3-month period. Wilcoxon signed-rank tests showed significant practice effects for 6 of 14 outcome measures with effect sizes ranging from negligible to medium (Hedge\'s g: .15-.40; Cliff\'s delta: .09-.39). The Spatial Working Memory test, Attention Switching Task, and Rapid Visual Processing test were the only tests with scores of adequate test-retest reliability. For all outcome measures, Pearson\'s and Spearman\'s correlation coefficients ranged from .39 to .79. The measurement error surrounding difference scores was large, thus requiring large changes in performance (i.e., 1-2 SDs) in order to interpret a change score as reliable. In the regression equations, test scores from initial testing significantly predicted retest scores for all outcome measures. Age was a significant predictor in several of the equations, while education was a significant predictor in only two of the equations. The adjusted R2 values ranged between .19 and .67. The present study provides results enabling clinicians to make probabilistic statements about change in cognitive functions based on CANTAB test performances.

BACKGROUND: Computerized Neurocognitive Testing (CNT) is frequently used for serial assessment of athletes following concussion. The Immediate Post-Concussion Assessment for Cognitive Testing (ImPACT) is a commonly used CNT with well-documented test-retest reliability in healthy samples for intervals ranging from one month to two years. However, previous research has not explored use of ImPACT for other serial testing methodologies such as immediately before and after an experimental trial/intervention where administration on the same day may be necessary.
OBJECTIVE: To examine the suitability of ImPACT for short-term, serial assessment of neurocognitive functioning.
METHODS: Prospective, repeated measures research design.
METHODS: Forty-two healthy, college-aged individuals completed ImPACT twice, with a one-hour break between assessments. Reliability was assessed using Pearson correlation coefficients, intraclass correlation coefficients (ICCs), reliable change indices (RCIs) and regression-based methods (RBM).
RESULTS: No significant increases in mean ImPACT composite or symptom scores were observed between assessments. ICCs ranged from 0.34 to 0.74 (single)/0.51 to 0.85 (average). Across two test administrations, 92-100% and 93-98% of participants\' change scores fell within cutoffs when utilizing the RCI and RBM, respectively.
CONCLUSIONS: The ICCs for ImPACT composite and factor scores across the one-hour administration were consistent with previous studies. Only a small percentage of scores fell outside of RCI and RBM cutoffs. These statistical metrics suggest that ImPACT has sufficient reliability when repeating administration within one-hour.

OBJECTIVE: Neurobehavioural disability (NBD) after acquired brain injury (ABI) is often associated with poor outcome. The \"St Andrew\'s-Swansea Neurobehavioural Outcome Scale\" (SASNOS) was developed to measure NBD in a range of applications. Two of the \"holy trinity\" of psychometric properties, reliability and validity, have been comprehensively mapped, but the extent to which SASNOS meets the third, responsiveness, has not been investigated. Demonstrating responsiveness is essential in instruments employed in repeated measurement scenarios to confirm their ability to discriminate real change from error. However, there is no single agreed method for determining responsiveness. For some instruments, this property remains unexplored. A difference in scores attaining statistical significance for aggregate data is frequently cited as support for this construct, but this approach remains heavily criticized. This study explores responsiveness of SASNOS.
METHODS: Consecutive SASNOS assessments completed over varying times for 145 individuals participating in neurobehavioural rehabilitation, drawn from multiple services, were compiled into a retrospective sample of convenience. Multiple methods were employed to confirm internal responsiveness, including those identifying statistically significant change, minimally detectable change and minimally important change.
RESULTS: All methods confirmed responsiveness as a psychometric property of SASNOS; the extent depended on method used and NBD domain investigated. A number of indicators are presented, which equip clinicians and researchers with options to interpret results from repeated assessments, including the individual level in the context of rehabilitation.
CONCLUSIONS: SASNOS reliably measures change over time in NBD symptoms, further confirming its suitability as an instrument for investigating multidimensional outcomes of ABI.

OBJECTIVE: Several reliable change indices (RCIs) exist to evaluate statistically significant individual change with repeated neuropsychological assessment. Yet there is little guidance on model selection and subsequent implications. Using existing test-retest norms, key parameters were systematically evaluated for influence on different RCI models.
METHODS: Normative test-retest data for selected Wechsler Memory Scale-IV subtests were chosen based on the direction and magnitude of differential practice (inequality of test and retest variance). The influence of individual relative position compared to the normative mean was systematically manipulated to evaluate for predictable differences in responsiveness for three RCI models.
RESULTS: With respect to negative change, RCI McSweeny was most responsive when individual baseline scores were below the normative mean, irrespective of differential practice. When an individual score was greater than the normative mean, RCI Chelune was most responsive with lower retest variance, and RCI Maassen most responsive with greater retest variance. This pattern of results can change when test-retest reliability is excellent and there is greater retest variability. Order of responsiveness is reversed if positive change is of interest.
CONCLUSIONS: RCI models tend to agree when the individual approximates the normative mean at baseline and test-retest variability is equal. However, no RCI model will be universally more or less responsive across all conditions, and model selection may influence subsequent interpretation of change. Given the systematic and predictable differences between models, a more rationale choice can now be made. While a consensus on RCI model preference does not exist, we prefer the regression-based model for several reasons outlined.

OBJECTIVE: The ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing) neurocognitive testing battery is a widely used tool used for the assessment and management of sports-related concussion. Research on the stability of ImPACT in high school athletes at a 1- and 2-year intervals have been inconsistent, requiring further investigation. We documented 1-, 2-, and 3-year test-retest reliability of repeated ImPACT baseline assessments in a sample of high school athletes, using multiple statistical methods for examining stability.
METHODS: A total of 1,510 high school athletes completed baseline cognitive testing using online ImPACT test battery at three time periods of approximately 1- (N = 250), 2- (N = 1146), and 3-year (N = 114) intervals. No participant sustained a concussion between assessments.
RESULTS: Intraclass correlation coefficients (ICCs) ranged in composite scores from 0.36 to 0.90 and showed little change as intervals between assessments increased. Reliable change indices and regression-based measures (RBMs) examining the test-retest stability demonstrated a lack of significant change in composite scores across the various time intervals, with very few cases (0%-6%) falling outside of 95% confidence intervals.
CONCLUSIONS: The results suggest ImPACT composites scores remain considerably stability across 1-, 2-, and 3-year test-retest intervals in high school athletes, when considering both ICCs and RBM. Annually ascertaining baseline scores continues to be optimal for ensuring accurate and individualized management of injury for concussed athletes. For instances in which more recent baselines are not available (1-2 years), clinicians should seek to utilize more conservative range estimates in determining the presence of clinically meaningful change in cognitive performance.

Computerized neurocognitive tests are frequently used to assess pediatric sport-related concussions; however, only 1 study has focused on the test-retest reliability of the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) in high school athletes and age influences have largely been ignored. Therefore, the purpose was to investigate the test-retest reliability of ImPACT and underlying age influences in a pediatric population. Two hundred (169 men and 31 women) youth ice hockey players completed ImPACT before/after a 6-month season. Reliability was assessed using Pearson correlation coefficients, intraclass correlation coefficients (ICCs), and regression-based methods (RBz). ICCs for the sample ranged from .48 to .75 (single)/.65 to .86 (average). In general, the older athletes (15-18: Single/Average ICCs = .35-.75/.52-.86) demonstrated greater reliability across composites than the younger athletes (11-14: Single/Average ICCs = .54-.63/.70-.77). Although there was variation in athletes\' performance across two test administrations, RBz revealed that only a small percentage of athletes performed beyond 80%, 90%, and 95% confidence intervals. Statistical metrics demonstrated reliability coefficients for ImPACT composites in a pediatric sample similar to previous studies, and also revealed important age-related influences.

Practice effects are improvements in cognitive test scores due to repeated exposure to the same tests. Typically viewed as error, short-term practice effects have been shown to provide valuable clinical information about diagnosis, prognosis, and treatment outcomes in older patients with mild cognitive impairments. This study examined short-term practice effects across one week and brain hypometabolism on fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) in 25 older adults (15 intact, 10 Mild Cognitive Impairment). Averaged cerebral brain metabolism on FDG PET was correlated with multiple cognitive scores at baseline in those with Mild Cognitive Impairment, and short-term practice effects accounted for additional variance in these same subjects. The relationship between brain metabolism and cognition (either at baseline or practice effects) was minimal in the intact individuals. Although needing replication in larger samples, short-term practice effects on tests of executive functioning and memory may provide valuable information about biomarkers of Alzheimer\'s disease.