Abstract: Objective To analyze the differential item functioning (DIF) of Fine Motor Function Measure (FMFM) between hemiplegic and non-hemiplegic cerebral palsy.Methods Data of children with cerebral palsy diagnosed by Rehabilitation Center of Children's Hospital of Fudan University and Children Rehabilitation Collaboration Network of Children's Hospital from 2001 to 2018 were collected and assessed by FMFM as well. The contralateral data of hemiplegic children were extracted from FMFM evaluation data, and 30% samples were randomly selected as focus group samples of DIF. According to the proportion of non-hemiplegic type and hemiplegic type in the whole sample, randomized stratified matching was used to match the control group sample. Conquest software was used to make Rasch analysis of the two groups of merged data samples and all 56 items in B to E area of FMFM, and single-handed items and double-handed items were separated by analysis item functioning. The single dimensionality of the scale was determined by the mean square of cohesive fit (Infit), the standard was MnSq 0.6-1.4, and differential item functioning of all 56 items and both single and double-handed items were analyzed.Results Tetally 3,442 times of FMFM assessments of 1,556 children with cerebral palsy were taken as whole samples and data. One hundred and ninety-eight FMFM assessments of focus group and 792 FMFM assessments of control group were included in this study. Single sample pairing test showed that there was no significant difference in FMFM scores between the two groups [112 (96, 146) vs 113 (95, 145)]. After three turns of item functioning analysis, 30 were classified as single-handed items and 26 as double-handed items. The absolute value >0.5 of the difference between the numerical of difficulty scale pair of total 56 items is 41. The absolute value >0.5 of the difference between the numerical of difficulty scale pair of 30 single-handed and 26 double-handed items are 23 (76.7%) and 9 (34.6%) respectively.Conclusion There exists DIF between hemiplegic and non-hemiplegic cerebral palsy in all 56 items of FMFM scale, especially in single-handed items. In order to accurately evaluate the fine motor function of hemiplegic children, it is necessary to re-establish the evaluation criteria and procedures.

Key words: Cerebral palsy, Difference of item functioning, Fine motor, Function assessment