PSYCHOMETRIC PROPERTIES OF A VASCULAR NEUROPSYCHOLOGICAL BATTERY FOR ASSESSING COGNITIVE FUNCTIONS AMONG STROKE SURVIVORS IN SOUTH-WEST NIGERIA

Abstract

Background: Nigeria, the most populous black nation in the world, stands to risk the further straining of its resources as a result of the increasing prevalence of stroke and other cardiovascular diseases. After stroke, very many survivors encounter issues bordering on cognitive impairments which are assessed by neuropsychological battery. However, Psychometric properties explain the reliability and validity of these instruments used to assess the consistency, dependability and accuracy of the test results obtained. Several studies have investigated the psychometrics of these neuropsychological batteries among stroke survivors. However, none has investigated the psychometrics of the instruments used in the COGFAST – NIGERA (Memory After Stoke) Study. Therefore, this study primarily assesses the psychometric properties of a vascular neuropsychological test battery for memory function among stroke survivors.

Methodology: Secondary data was obtained from two referral hospitals from the records of 381 consecutively presenting stroke patients who are 45 years old or older made up of 244 stroke survivors and 137 healthy controls who were also clinically diagnosed by experienced physician neurologists were recruited from stroke registers of the two specialist hospitals in Abeokuta and Ibadan. The COGFAST-NG Study was conducted between July, 2010 and June, 2012. The psychometric properties of the test battery were investigated by assessing the internal consistency reliability using the Cronbach’s Alpha model and the Nunnaly’s criterion. Validity of the instrument was assessed using the Receiver Operating Characteristic curve analysis and the spearman’s correlation coefficients. The factor structure of the test battery was described using the principal components analysis through the varimax rotation method. Analyses of data were performed using the SPSS Version 25 software.

Results: There was no statistically significant difference between the ages, gender and education years between the two groups. Scores recorded after administering the tests on participants of the study showed that there were significant differences in the mean score of some tests except with a few showing no significance. The stroke survivors and the control group had Cronbach’s Alpha of 0.750 and 0.647 respectively. The Area under the Receiver Operating Characteristic curve (AUC) ranged between 0.480 and 0.722. The sensitivity and specificity of the statistically significant tests ranged between 51.4 – 69.7% and 56.9 – 65% respectively with reasonable cut-points. Correlations between the MMSE and majority of the tests proved to be moderately strong ranging from 0.339 – 0.651. A three-factor solution accounting for 56.1% of the total variance for all the participants while also, a three-factor solution was recorded for the study group with 56.8% of the total variance explained. The control group showed a four-factor solution with 62.8% of the variance explained.

Conclusion: The study has shown that the V-NB demonstrated good internal consistency reliability. The validity study of the test battery has some attributes of accuracy and usefulness for screening individuals suspected to have cognitive impairment. The test battery also demonstrated an acceptable internal structure with reasonable factor loadings. Very importantly, this study proposed cut-points for some tests in the battery for the purpose of screening patients for cognitive impairments but cautioned that the cut-points might not be necessarily useful for diagnostics.