Development of a functional movement scale for infants.

The increasing survival rate of infants with a complicated birth and perinatal history generated the need for a test of functional motor performance with the capability of identifying children under four months of age with delayed development which could be addressed with physical therapy. This paper describes a Rasch analysis of the psychometric qualities of the Test of Infant Motor Performance (TIMP) for the purpose of reducing the length of the test while maintaining its precision as a measurement device. Following analysis of fit statistics, item-to-total correlations, redundancy of item difficulty measures, and consideration of clinically-relevant features of test items from analysis of 1732 tests, the TIMP was reduced from 59 to 42 items forming a functional motor scale for prematurely born infants. The resulting person separation index was 4.85 and the item separation index was 23.79.