Objective: To compare whether stage-specific and fixed minimal detectable change (MDC) thresholds yield different classifications of apparent change in repeated within-session 10-meter walk test (10MWT) and Timed Up and Go test (TUG) measurements in patients with Parkinson’s disease (PD).
Background: MDC is used to determine whether an observed change represents true change. In PD, published MDC thresholds for the 10MWT and TUG vary depending on whether they are specific to Hoehn and Yahr (H&Y) stage or fixed across stages. How these different thresholds influence change classification when applied to the same dataset remains unclear.
Method: Within-session 10MWT and TUG data (2 trials each) were analyzed in 95 patients with PD (65.6 ± 7.9 years, 54 female) at H&Y stages II–IV: II (n=28), III (n=40), IV (n=27). This sample included additional participants enrolled after our previous study [1]. No intervention occurred between trials; true change was not expected. For the 10MWT, stage-specific MDCs [1] were compared with the fixed MDC of Combs et al. (0.09 m/s) [2]. For the TUG, stage-specific MDCs [1] were compared with intra-session MDCs of Luque-Casado et al. (1.21 s and 1.28 s) [3]. Participants were classified as MDC-exceeding or non-exceeding. Paired classifications were compared by stage using exact McNemar tests.
Results: Exceedance rates are reported as stage-specific vs fixed MDC. For the 10MWT, the fixed threshold tended to yield higher rates of apparent change classification, though not significantly: H&Y II, 7.1% vs 14.3% (p=0.500); III, 5.0% vs 15.0% (p=0.125); IV, 3.7% vs 14.8% (p=0.250). For the TUG, no significant difference was found in H&Y II or III: H&Y II, 7.1% vs 0% for both fixed thresholds (p=0.500); III, 7.5% vs 10.0% for 1.21 s (p=1.000) and 7.5% vs 7.5% for 1.28 s (p=1.000). In H&Y IV, fixed thresholds yielded significantly higher rates: 3.7% vs 33.3% for both (p=0.0078).
Conclusion: Fixed MDC thresholds tended to increase apparent change detection, most notably for the TUG in H&Y IV, suggesting differences in apparent change classification despite no intervention. Stage-specific MDCs may reduce such differences in classification. However, the compared thresholds were derived from differing protocols (e.g., trials and conditions), which may partly explain discrepancies, warranting cautious interpretation.
References: 1. Yamasaki R, Inoue Y (2026). Does the Minimal Detectable Change in the 10-Meter Walk Test and Timed Up and Go Test Differ by Parkinson’s Disease Severity? Arch Phys Med Rehabil. Online ahead of print. doi: 10.1016/j.apmr.2026.01.010. PMID: 41558572.
2. Combs SA, Diehl MD, Filip J, Long E (2014). Short-distance walking speed tests in people with Parkinson disease: reliability, responsiveness, and validity. Gait Posture. 39(2): 784-788. PMID: 24246801.
3. Luque-Casado A, Novo-Ponte S, Sánchez-Molina JA, Sevilla-Sánchez M, Santos-García D, Fernández-Del-Olmo M (2021). Test-Retest Reliability of the Timed Up and Go Test in Subjects with Parkinson’s Disease: Implications for Longitudinal Assessments. J Parkinsons Dis. 11(4): 2047-2055. PMID: 34334420.
To cite this abstract in AMA style:
R. Yamasaki, Y. Inoue. Apparent Change Classification with Stage-Specific and Fixed Minimal Detectable Change Thresholds in Parkinson’s Disease [abstract]. Mov Disord. 2026; 41 (suppl 1). https://www.mdsabstracts.org/abstract/apparent-change-classification-with-stage-specific-and-fixed-minimal-detectable-change-thresholds-in-parkinsons-disease/. Accessed October 1, 2026.« Back to 2026 International Congress
MDS Abstracts - https://www.mdsabstracts.org/abstract/apparent-change-classification-with-stage-specific-and-fixed-minimal-detectable-change-thresholds-in-parkinsons-disease/