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Published on: December 16, 2022
Minimum Detectable Change and Minimal Clinically Important Difference for the Box and Block Test and Fugl-Meyer
David Aaby1, Jane E Sullivan2, Carolina Carmona2
1Department of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL.
Objectives:
To quantify the Minimum Detectable Change (MDC) and the Minimal Clinically Important Difference (MCID) of the Box and Blocks Test (BBT) and Upper Extremity Fugl-Meyer Assessment (FMA-UE), and to determine whether there is a BBT floor effect for individuals with chronic stroke and moderate to severe motor impairment.
Design:
Analysis of pre- and postinterventional data using anchor and distribution-based methods.
Setting:
Research laboratory.
Participants:
Fifty-three adults (N=53) with chronic stroke. Age (mean ± SD)=58.5±10.7; 71% men; mean time poststroke=7.4±6.8 years; baseline FMA=20.6±7.6.
Interventions:
Randomized controlled trial, including 24 sessions over 8 weeks. Each session included 40 trials of reach-grasp-retrieve-release practice using the ReIn-Hand, with or without robotic support of the arm weight.
Main Outcome Measures:
A BBT floor effect emerged among participants with baseline FMA-UE (FMAbl)≤18. Above this threshold, the linear regression model reported that for every 1-unit increase in FMAbl, MDC for the BBT (MDCBBT) increased by 0.46 blocks/min. MDC for the FMA (MDCFMA) followed a concave quadratic pattern with FMAbl, increasing until reaching a peak when FMAbl was 21-26, then declining. Global Rating of Change was not correlated with changes in BBT (ρ=0.22; P=.29) or FMA (ρ=0.19; P=.23). Using distribution-based methods, we found that MCID for the BBT (MCIDBBT) increased linearly with baseline FMA-UE: for every 10-unit increase in FMAbl, MCIDBBT increased by 1 block/min. There is no linear relationship between baseline FMA-UE and MCIDFMA. Overall MCIDFMA=2.1 points.
Conclusions:
Because of its floor effect, the BBT may not be appropriate for those with severe motor impairment poststroke. MDC values for both BBT and FMA-UE depend on motor impairment severity and should be interpreted using regression model-based estimates. In valid ranges of BBT and FMA-UE, subjective perceived change (Global Rating of Change) showed limited association with them. Distribution-based MCID values were small but meaningful, though they may not reflect participants' perceived importance.
