Validity of the test of infant motor performance for prediction of 6-, 9- and 12-month scores on the Alberta Infant Motor Scale

The Test of Infant Motor Performance (TIMP) is a test of functional movement in infants from 32 weeks' post-conceptional age to 4 months post-term. The purpose of this study was to assess in 96 infants (44 females, 52 males) with varying risk, the relation between measures on the TIMP at 7, 30, 60, and 90 days after term age and percentile ranks (PR) on the Alberta Infant Motor Scale (AIMS). Correlation between scores on the TIMP and the AIMS was highest for TIMP tests at 90 days and AIMS testing at 6 months (r=0.67,p=0.0001), but all comparisons were statistically significant except those between the TIMP at 7 days and AIMS PR at 9 months. In a multiple regression analysis combining a perinatal risk score and 7-day TIMP measures to predict 12-month AIMS PR, risk, but not TIMP, predicted outcome (21% of variance explained). At older ages TIMP measures made increasing contributions to prediction of 12-month AIMS PR (30% of variance explained by 90-day TIMP). The best TIMP score to maximize specificity and correctly identify 84% of the infants above versus below the 10th PR at 6 months was a cut-off point of 1 SD below the mean. The same cut-off point correctly identified 88% of the infants at 12 months. A cut-off of -0.5 SD, however, maximized sensitivity at 92%. A negative test result, i.e. score above -0.5 SD at 3 months, carried only a 2% probability of a poor 12-month outcome. We conclude that TIMP scores significantly predict AIMS PR 6 to 12 months later, but the TIMP at 3 months of age has the greatest degree of validity for predicting motor performance on the AIMS at 12 months and can be used clinically to identify infants likely to benefit from intervention.