Determining clinically meaningful change: minimal clinically important difference for common depression scales in older adults with parkinson’s disease

BACKGROUND: The Minimal Clinically Important Difference (MCID) is a crucial measure in clinical research, reflecting the smallest change in symptoms that patients perceive as beneficial. While MCID values have been established for various symptoms in Parkinson's disease (PD), they remain underexplored in the context of depression. OBJECTIVE: This study aims to determine MCID values for three commonly used depression scales in PD: The Beck Depression Inventory (BDI-II), the Hospital Anxiety and Depression Scale - Depression subscale (HADS-D), and the 15-item Geriatric Depression Scale (GDS-15). METHODS: A total of 112 individuals with PD and depression (mean age = 70.91 ± 3.12 years) participated in a 10-week cognitive behavioral therapy program. The MCID values were estimated using both distribution-based and anchor-based methods. The Global Rating of Change (GRoC) scale was used as an anchor to assess perceived changes in depressive symptoms. RESULTS: MCID values were refined using the mean difference approach, resulting in the following: -5.79 points for the BDI-II, -3.52 points for the HADS-D, and - 3.05 points for the GDS-15, all with statistical significance (p < 0.001). Using Youden's index, the optimal MCID cut-off values were ≤ -3 points for BDI-II, ≤ -2 points for HADS-D, and ≤ -2 points for GDS-15, with high sensitivity and specificity for each. The MCID values derived from the distribution-based method for the BDI-II, HADS-D, and GDS-15 were 5.57-3.55, 1.11-3.07, and 0.96-2.66 points, respectively. CONCLUSIONS: This study establishes MCID thresholds for commonly used depression scales in PD. These benchmarks are essential for improving clinical decision-making and evaluating the effectiveness of interventions in both clinical and research settings.