Defining a Universal Measurement Scale and Standardized Unit for Fine Motor Development.

OBJECTIVE

To develop a construct specification equation (CSE) that identifies the task characteristics most strongly associated with fine motor item difficulty, establish a standardized unit, the fine motor unit (FMU), and define a universal measurement scale.

STUDY

DESIGN

Cross-sectional design.

SETTING

General community.

PARTICIPANTS

Secondary analysis of a convenience sample of children (n=637) under 71 months in Brazil. Children were excluded for musculoskeletal disorders, genetic syndromes, and congenital malformation. The average age was 21.7 months (18.6mo), and 51% were female.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Peabody Developmental Motor Scales-Second edition (PDMS-2) Grasp Scale.

RESULTS

Explanatory factors with corresponding ordinal rating systems for fine motor development were created from task analysis and theory. Explanatory factors included shoulder/elbow/wrist movement, hand/fingers grasp, body position, object description, and cueing. Each item on the PDMS-2 Grasping Scale was rated across all explanatory variables. Explanatory variables had strong linear associations with previously published Rasch measurement item calibrations for the PDMS-2 Grasping Scale items. Forward stepwise linear regression tested the ability of explanatory variables to explain the variance in PDSM-2 item calibrations. Three models explained between 88% and 90% of the variance in PDMS-2 Grasping Scale item calibrations. The most parsimonious model included the shoulder/elbow/wrist movement and the hand/finger explanatory factors. This model was used as the CSE and anchored to items Grasp Reflex and Dynamic Marker Grasp. This established a standardized unit, the FMU, as 1/100th of the distance between each anchor. FMUs had a positive linear association with item calibrations (r=.93; P<.01).

CONCLUSIONS

The findings support CSE methodology for investigating explanatory factors related to fine motor development. The results of this study suggest that a CSE can provide initial support for validating a universal measurement scale and standardized unit for fine motor development.