title: Examining measurement properties of cognitive screening instruments used post-stroke
Creators: name: Elliott, Emma P.J.
Publisher: name: University of Glasgow
Year: 2021

description: Background: Cognitive screening after a stroke is recommended by clinical guidelines, specialist societies and as part of national audit programs. However, due to vague recommendations, different cognitive syndromes, and differing opinions regarding cognitive screening instrument (CSI) choice and timing, a range of CSIs are being used in clinical practice and research. There are limited data related to the use of both brief CSIs (administered in ≤5 minutes) and stroke-specific CSIs. This means that some teams may be using CSIs without any supportive evidence that they are fit for purpose. I aimed to examine measurement properties of different brief generic CSIs and the Oxford Cognitive Screen (OCS). Methods: I first conducted a study into the feasibility of various brief CSIs on a hyper acute stroke unit; I examined the completion rates, reasons for being untestable and examined associations with being untestable. I conducted two systematic reviews of test accuracy; one to identify and evaluate shortened versions of the Montreal Cognitive Assessment (SF-MoCA) and the second to evaluate telephone-based CSIs. Using the data from the Assessing Post-Stroke Psychology Longitudinal Evaluation study (APPLE), I examined completion rates and floor/ceiling effects of a range of brief CSIs and the OCS. I examined the accuracy of brief CSIs to detect prestroke cognitive impairment (against diagnosis in medical records) and to detect post-stroke single and multi-domain cognitive impairment, using the OCS as a reference standard. Finally, I investigated whether domain-specific results from the OCS completed at one-month post-stroke were associated with functional, mood and quality of life outcomes at six months. Findings: A quarter of participants were untestable on at least one cognitive test item. Across the different CSIs examined, the clock drawing test (CDT) had the lowest completion rate, whereas there were no missing data using the 4 A’s Test (4AT), due to scoring for untestable being incorporated. In the first systematic review I identified thirteen SF-MoCAs. Across the published literature and in the external validation, the performance of the short forms varied but demonstrated a pattern of high sensitivity to detect multidomain cognitive impairment, according to different reference standards. In the second systematic review I identified 15 telephone-based CSIs to identify MCI or dementia. Four of these CSIs were used in participants post-stroke (Telephone Interview for Cognitive Status [TICS], TICS-modified, TelephoneMontreal Cognitive Assessment [T-MoCA], T-MoCA short). Of the limited data available in stroke, the telephone CSIs demonstrated high sensitivity to detect multi-domain cognitive impairment. Outside of stroke, the TICS and TICS-m had the greatest supportive evidence base to screen for dementia. In the APPLE study, ceiling effects were highest for the Abbreviated Mental Test (AMT-4), Cog-4 and 4AT. Across eight brief CSIs, the pattern of accuracy for preand post-stroke cognitive syndromes was generally low sensitivity, high specificity, apart from the CDT and NINDS-CSN 5-min MoCA which exhibited the opposite pattern. The OCS had good completion rates, but fewer participants fully completed it in comparison to the brief CSIs. There were no issues of floor/ceiling effects. In unadjusted models, all OCS domains apart from memory were significantly associated with at least one six-month outcome. However, when controlling for confounding variables (such as age, education, pre-stroke disability and stroke severity), and adjusting for multiple testing, only one domain remained significant with one outcome: executive dysfunction had a modest association with reduced quality of life (measured using the EQ-5D). Conclusions: To summarise, in the context of stroke, incomplete cognitive screening assessments should be expected. CSIs with fewer items or stroke specific CSIs do not necessarily have a higher completion rate. Clinicians and researchers should therefore make a-priori plans on how to address incomplete assessments. Recommendations for CSI choice differ depending on the purpose of screening, including resources and plans for following up those with identified cognitive impairment. Most brief CSIs demonstrated low sensitivity, high specificity to detect post-stroke multi-domain cognitive impairment so would not be recommended for clinical use. Telephone-based CSIs have some promising initial data in the stroke context, but further studies are needed before recommending for clinical use. There was insufficient evidence that results from the OCS at one month are associated with functional and mood outcomes at six months, but some evidence that executive dysfunction is independently associated with reduced quality of life. Further studies are necessary to understand the prognostic utility of the OCS.