Hallucinations are common and distressing in Parkinson’s disease, but the minimum clinically important difference (MCID) for two key rating tools—the Scale for Assessment of Positive Symptoms-Hallucinations (SAPS-H) and the University of Miami PD Hallucinations Questionnaire (UM-PDHQ)—had not been defined. MCID, the smallest score change patients and clinicians perceive as meaningful, guides both trial design and clinical decision-making. Researchers of this study set out to establish MCID ranges using both expert consensus (Delphi) and statistical methods. By defining what constitutes a meaningful change, the work aims to align outcome interpretation between trials and everyday care.
Across three Delphi rounds, 51 clinicians/researchers and 16 people with lived experience reached consensus that a 2-point change is clinically meaningful on both scales. Consensus was predefined as at least 75% agreement across panels. Using blinded data from the first 100 participants in the TOP HAT trial, distribution-based MCIDs were 2.6 points (SAPS-H) and 1.3 points (UM-PDHQ). Anchor-based MCIDs (1-point CGI-S improvement) were 2.1 and 1.3 points, respectively. Triangulating methods, the estimated MCID ranges were 2.0 to 2.7 points for SAPS-H and 1.3 to 2.0 points for UM-PDHQ. The convergence of consensus- and data-driven estimates strengthens confidence in these thresholds. These thresholds offer practical benchmarks for powering studies, evaluating treatment effects, and standardizing reporting across PD hallucination trials.
Reference: Reeves S, Mahdi J, Appleby M, et al. Minimal clinically important differences for treatment of hallucinations in Parkinson’s disease and dementia with Lewy bodies. Psychol Med. 2025;55:e93. doi: 10.1017/S0033291725000534.
