Reliability of cognitive tests of ELSA-Brasil, the brazilian longitudinal study of adult health

Cognitive function evaluation entails the use of neuropsychological tests, applied exclusively or in sequence. The results of these tests may be influenced by factors related to the environment, the interviewer or the interviewee. OBJECTIVES: We examined the test-retest reliability of some tests of the Brazilian version from the Consortium to Establish a Registry for Alzheimer's disease. METHODS: The ELSA-Brasil is a multicentre study of civil servants (35-74 years of age) from public institutions across six Brazilian States. The same tests were applied, in different order of appearance, by the same trained and certified interviewer, with an approximate 20-day interval, to 160 adults (51% men, mean age 52 years). The Intraclass Correlation Coefficient (ICC) was used to assess the reliability of the measures; and a dispersion graph was used to examine the patterns of agreement between them. RESULTS: We observed higher retest scores in all tests as well as a shorter test completion time for the Trail Making Test B. ICC values for each test were as following: Word List Learning Test (0.56), Word Recall (0.50), Word Recognition (0.35), Phonemic Verbal Fluency Test (VFT, 0.61), Semantic VFT (0.53) and Trail B (0.91). The Bland-Altman plot showed better correlation of executive function (VFT and Trail B) than of memory tests. CONCLUSIONS: Better performance in retest may reflect a learning effect, and suggest that retest should be repeated using alternate forms or after longer periods. In this sample of adults with high schooling level, reliability was only moderate for memory tests whereas the measurement of executive function proved more reliable.