Minimal Clinically Important Differences of Common Anxiety Scales in Older Adults with Parkinson’s Disease with Anxiety Following Cognitive Behavioral Therapy

OBJECTIVES: To establish minimal clinically important difference (MCID) thresholds for the Beck Anxiety Inventory (BAI), Hospital Anxiety and Depression Scale-Anxiety Subscale (HADS-A), Parkinson's Anxiety Scale (PAS), and Geriatric Anxiety Inventory (GAI) in older adults with Parkinson's disease and anxiety (PD-A), and identify optimal thresholds for classifying clinical improvement. METHODS: This cohort study included 110 older adults with PD-A who completed individualized Cognitive-Behavioral Therapy (CBT). Anxiety was assessed before and after intervention using the four scales. Clinical change was anchored to the Global Rating of Change (GRoC) scale. MCIDs were estimated using anchor- and distribution-based methods. RESULTS: Anchor-based between-group mean-change estimates yielded MCIDs of -2.38 (BAI), -3.64 (HADS-A), -3.13 (PAS), and -2.95 (GAI). Receiver operating characteristic analysis using the Youden index identified complementary classification cut-offs of ≤ -2 for the BAI, HADS-A, and PAS, and ≤ -1 for the GAI. CONCLUSIONS: This study provides MCID thresholds for four anxiety measures in older adults with PD-A, offering clinically relevant benchmarks for interpreting treatment-related changes and evaluating improvement. CLINICAL IMPLICATIONS: Clinicians can use the estimated MCID thresholds to interpret whether changes in anxiety scores following CBT are likely to represent clinically meaningful improvement in older adults with PD-A. The complementary ROC-derived cutoffs may assist in identifying individual improvement, while combined use of anxiety measures, particularly the PAS and HADS-A, may enhance sensitivity to clinically meaningful change.