Test Accuracy of Cognitive Screening Tests for Diagnosis of Dementia and Multidomain Cognitive Impairment in Stroke

Abstract

S troke-survivors are at particular risk of cognitive decline. Three month dementia prevalence is ≥30%, and even minor stroke events have cognitive sequel.1,2 Poststroke cognitive impairment is associated with increased mortality, disability, and institutionalization. 3 The importance of cognitive change is highlighted by stroke-survivors themselves. In a national priority setting exercise, cognitive impairment was voted the single most important topic for stroke research. 4 A first step in management of cognitive problems is recognition and diagnosis. Informal clinician assessment will miss important cognitive problems, 5 and formal cognitive testing is recommended. [6][7][8] The ideal would be expert, multidisciplinary assessment informed by comprehensive investigations. This approach is not feasible at a population level. In practice, a 2-step system is adopted, with baseline cognitive testing used for screening or triage and specialist assessment to define the cognitive problem offered depending on the results.Although there is general agreement on the merits of poststroke cognitive assessment, there is no consensus on a preferred testing strategy. [6][7][8] Various cognitive screening tools are available with substantial variation in test used. 9,10 The clinical meaning of cognitive problems after stroke will vary according to test context. Cognitive impairment diagnosed in the first days post stroke may reflect a mix of delirium, strokespecific impairments, and prestroke cognitive decline. 2,11,12 In the longer term, assessments aim to make or refute a dementia diagnosis. Common to all test situations is a final diagnosis of presence/absence of clinically important impairments. A screening assessment should detect this clinical syndrome of all-cause, poststroke multidomain cognitive impairment.Background and Purpose-Guidelines recommend screening stroke-survivors for cognitive impairments. We sought to collate published data on test accuracy of cognitive screening tools. Methods-Index test was any direct, cognitive screening assessment compared against reference standard diagnosis of (undifferentiated) multidomain cognitive impairment/dementia. We used a sensitive search statement to search multiple, crossdisciplinary databases from inception to January 2014. Titles, abstracts, and articles were screened by independent researchers. We described risk of bias using Quality Assessment of Diagnostic Accuracy Studies tool and reporting quality using Standards for Reporting of Diagnostic Accuracy guidance. Where data allowed, we pooled test accuracy using bivariate methods. Results-From 19 182 titles, we reviewed 241 articles, 35 suitable for inclusion. There was substantial heterogeneity: 25 differing screening tests; differing stroke settings (acute stroke, n=11 articles), and reference standards used (neuropsychological battery, n=21 articles). One article was graded low risk of bias; common issues were case-control methodology (n=7 articles) and missing data (n=22 Lees et al Cognitive Screening in S...

Validating a Pragmatic Approach to Cognitive Screening in Stroke Prevention Clinics Using the Montreal Cognitive Assessment

“…Comparing the MoCA to various criterion standards, studies report cut points that range from ≤25 to ≤19, with widely varying sensitivities and specificities. [10][11][12]15,17,[34][35][36][37] Cut points reported may vary based on the criterion standard chosen (reflecting mild, moderate-severe impairment, or dementia); however, even when criterion standards are similar among studies, resulting cut points are not uniform. This variability in cut points stems, in part, from the heterogeneity inherent in screening cognition.…”

“…[10][11][12]15,17,[34][35][36][37] In clinical practice, many healthcare professionals thus define a score of ≤25 as abnormal. Yet 92% of participants scoring 23 to 27 were within 2 SD of normal on multiple neuropsychological test scores, suggesting a single cut point is not optimal for characterizing these participants and may artificially minimize the uncertainty inherent in screening for a complex phenomenon, such as cognition.…”

“…Indeed, a low MoCA does not necessarily correspond to greater cognitive severity-most validation studies have used MoCA to predict dichotomous outcomes (impaired or not) based on varying standards (differing cut points from 1 SD on a single test to 2 SDs on multiple domains across variable "gold standard" batteries), selection criteria, 14 sample sizes, and timeframes. 8,12,[15][16][17] Indeed, population normative data suggest that many people functioning normally in the community score <26. 18 A single cut point on the MoCA does not accurately diagnose across the range of cultures, ages, educations, and individual variables encountered in clinical or research environments.…”

Stroke Location Is an Independent Predictor of Cognitive Outcome

“…A favorable cognitive outcome was defined as a MoCA score >25. 25 By analogy, favorable cognitive outcome on the sMoCA was defined as sMoCA >20. Comparisons used parametric Student t tests or Mann-Whitney statistics when appropriate.…”

Methodological Factors in Determining Risk of Dementia After Transient Ischemic Attack and Stroke

“…Dementia was defined as pre-or postevent according to whether the diagnosis was made before or after the index event. 4 Postevent dementia diagnosis was made as described previously 4 and required mini-mental state examination<24 22 and remaining <24 for all subsequent follow-ups or MoCA<20 23 or telephone interview for cognitive status <22 21 or T-MoCA<9. 21 For subjects with an incomplete test (ie, testing was done, but there was a problem such as dysphasia, visual impairment, and inability to use the dominant arm), individual patient scores were reviewed: patients with cognitive scores above cut-off were designated as no-dementia.…”