Diagnosing dementia with cognitive tests: are demographic corrections useful?

• Main Author: O'Connell, Megan Eleine
• Other Authors: Tuokko, Holly
• Language: English; en
• Published: 2008
• Subjects: diagnostic accuracy; demographic corrections; dementia; sensitivity; specificity; UVic Subject Index::Humanities and Social Sciences; UVic Subject Index::Sciences and Engineering::Psychology::Cognitive psychology
• Online Access: http://hdl.handle.net/1828/298

Diagnostic biases against individuals of advanced age or few years of formal education exist because age and education are commonly related to performance on cognitive tests, thus, demographic corrections for these tests are used. Corrections are complicated, however, by an association between demographic variables and dementia diagnoses. This dissertation examined the dementia diagnostic accuracy of demographic corrections for cognitive tests. Experiment I tested whether, in the context of skewed tests that violate the statistical assumptions of linearity and homoscedasticity, the accuracy of demographically-corrected test scores would be reduced. Experiment II tested whether demographic corrections would only be appropriate for biased factors instead of the total score for multifactorial tests. Experiment III explored whether demographic corrections would be inappropriate under conditions where the dementia pathology overrides the association between cognitive test scores and demographic variables. Experiment IV explored whether demographic corrections would be inappropriate in conditions where the demographic variables were, in themselves, risk factors for dementia, as this would remove predictive variance. Experiment V explored aspects particular to regression-based demographic corrections that might adversely affect diagnostic accuracy. Experiments I to V were simulation-based; consequently Experiment VI explored replication of these findings using regression adjusted scores in a previously collected clinical database. Finally, Experiment VII used clinical data in conjunction with published clinical normative data with demographic-stratification to test the generalizability of these findings to clinical practice. Using area under the receiver operating characteristic curve comparisons, the use of demographically-corrected scores repeatedly failed to improve upon the dementia diagnostic accuracy of uncorrected cognitive test scores, regardless of whether these corrections were regression-based or based on demographically stratified normative data. Demographic corrections reduced dementia diagnostic accuracy when cognitive test scores were skewed or when adjustments were regression-based and demographic variables were risk factors for dementia. The use of demographic corrections when dementia pathology supersedes any association between cognitive test scores and demographic variables does not impact the relative diagnostic accuracy of demographically-corrected versus uncorrected test scores. Overall, these results suggest that the use of demographic corrections for cognitive test scores is highly cautioned when the goal is to maximize dementia diagnostic accuracy.