Measurement structure of the Wolf Motor Function Test: implications for motor control theory

Area of Science:

• Rehabilitation Science
• Motor Control
• Psychometrics

Background:

• Accurate measurement of post-stroke upper-extremity function is crucial for rehabilitation.
• The theoretical basis of assessment tools informs score interpretation.
• The Wolf Motor Function Test (WMFT) is a common outcome measure.

Purpose of the Study:

• To investigate the theoretical framework of the WMFT.
• To determine if WMFT items measure a single underlying trait.
• To examine the alignment between hypothesized and empirical item difficulty order.

Main Methods:

• Confirmatory Factor Analysis (CFA) and Rasch analysis were used.
• Data from 189 participants in the EXCITE trial were analyzed.
• One-factor and two-factor CFA models were compared.

Main Results:

• Both one-factor and two-factor CFA models showed comparable fit.
• The two-factor model indicated a strong interfactor correlation.
• Thirteen of fourteen items fit the Rasch model, with difficulty order matching hypotheses.

Conclusions:

• WMFT items appear to measure a single construct.
• The established item difficulty hierarchy supports theoretical models of stroke recovery.
• Findings enhance understanding of person ability versus task difficulty interactions.