Comparative performance of five cognitive screening tests in a large sample of seniors.

Abstract

Introduction Recent introductions of disease-modifying treatments for Alzheimer's disease have re-invigorated the cause of early dementia detection. Cognitive "Paper & pencil" tests represent the bedrock of clinical assessment, because they are cheap, easy to perform, and don't require brain imaging or biological testing. Cognitive tests vary greatly in duration, complexity, sociolinguistic biases, probed cognitive domains, and their specificity and sensitivity of detecting cognitive impairment (CI). Consequently, an ecologically valid head-to-head comparison seems essential for evidence-based dementia screening. Method We compared five tests: MoCA, ADAS, ACE-III, Eurotest, and Phototest on a large sample of seniors (N=456, 77.9 ± 8 years, 71% females). Their specificity and sensitivity was estimated in a novel way by contrasting each test's outcome to the majority outcome across the remaining tests (Comparative Specificity & Sensitivity Calculation - CSSC). This obviates the need for an a priori gold standard such as a clinically clear-cut sample of dementia/MCI/controls. We posit that the CSSC results in a more ecologically valid estimation of clinical performance while precluding biases resulting from different dementia/MCI diagnostic criteria, and the proficiency of detecting these conditions. Results There exists a stark trade-off between behavioral test specificity and sensitivity. The test with the highest specificity had the lowest sensitivity, and vice versa. The comparative specificities and sensitivities were, respectively: Phototest (97%, 47%), Eurotest (94%, 55%), ADAS (90%, 68%), ACE-III (72%, 77%), MoCA (55%, 95%). Conclusion Assuming a CI prevalence of 10%, the shortest (~3 min) and the simplest instrument - the Phototest, was shown to have the best overall performance (accuracy 92%, PPV 66%, NPV 94%).