Subjective Cognitive Complaints and Objective Cognitive Performance Across Diagnostic Groups in Memory Clinic Patients: A Cross-Sectional Comparison of the SCD-Q and CFQ Questionnaires

Background This study evaluated the diagnostic value and factorial structure of the Subjective Cognitive Decline Questionnaire (SCD-Q) and the Cognitive Failures Questionnaire (CFQ) in the context of early detection of cognitive decline in a memory clinic setting. Methods A total of 128 patients were included (AD/MCI: n = 50; non-AD dementia: n = 10; mixed dementia: n = 16; subjective cognitive decline [SCD]: n = 21). Participants completed the modified SCD-Q17 and CFQ and underwent standardized cognitive assessment. Principal component and cluster analyses, regression models, and ROC analyses were used to examine psychometric properties and diagnostic performance. Results The SCD-Q17 correlated with objective cognition (CERAD: r = −0.29 to −0.35, P = 0.023-0.005) and differentiated SCD from mixed dementia (AUC = 0.71). The CFQ primarily reflected executive and attentional failures and showed moderate discrimination for non-AD dementia (SCD vs NADD: AUC = 0.67). Cluster analyses identified 2 profiles (impaired vs unimpaired) for both instruments (κ = 0.47). PCA indicated a more redundant structure for the SCD-Q17, whereas the CFQ showed a broader multidimensional structure. Conclusions Relative to CERAD performance, both questionnaires distinguished cognitively impaired from unimpaired individuals, but neither provided sufficient precision to classify specific clinical entities.