Consequences of age and education correction of cognitive screening tests - A simulation study of the MoCA test in Italy.

Background: Cognitive screening tools are widely used in clinical practice to screen for age-related cognitive impairment and dementia. These tools' test scores are known to be influenced by age and education, leading to routine correction of raw scores for these factors. Despite these corrections being common practice, there is evidence suggesting that corrected scores may perform worse in terms of discrimination than raw scores.

Objective: To address the ongoing debate in the field of dementia research, we assessed the impact of the corrections on discrimination, specificity, and sensitivity of the Montreal Cognitive Assessment test in Italy, both for the overall population and across age and education strata.

Methodology: We created a realistic model of the resident population in Italy in terms of age, education, cognitive impairment and test scores, and performed a simulation study.

Results: We confirmed that the discrimination performance was higher for raw scores than for corrected scores in discriminating patients with cognitive impairment from individuals without (areas under the curve of 0.947 and 0.923 respectively). With thresholds determined on the overall population, raw scores showed higher sensitivities for higher-risk age-education groups and higher specificities for lower-risk groups. Conversely, corrected scores showed uniform sensitivity and specificity across demographic strata, and thus better performance for certain age-education groups.

Conclusion: Raw and corrected scores show different performances due to the underlying causal relationships between the variables. Each approach has advantages and disadvantages, the optimal choice between raw and corrected scores depends on the aims and preferences of practitioners and policymakers.