The purposes of this study were 1) to assess the relationship (concurrent validity) of scores at three months of age on a new scale, the Test of Infant Motor Performance (TIMP), with those on the Alberta Infant Motor Scale (AIMS) at the same age and 2) to determine the sensitivity and specificity of TIMP scores for classifying infants as above or below the 10th percentile on the AIMS (ie, agreement between the tests on low-scoring vs high-scoring infants). Ninety pairs of tests were performed on infants (n = 90) from nine to 18 weeks of age; 90% of the tests were completed within three days of each other. Eleven raters tested infants; 53% of the two tests on a given infant were conducted by different raters. The Pearson product moment correlation coefficient was used to assess the relationship between TIMP and AIMS raw scores or percentile ranks. The correlation between raw scores on the TIMP and the AIMS was 0.64 (p < 0.0001) and that between the TIMP raw scores and the AIMS percentile ranks was 0.60 (p < 0.0001). An analysis of the sensitivity and specificity of various TIMP cutoff scores for comparison with AIMS scores above and below the 10th percentile revealed that the best TIMP score that identified 80% of the infants correctly was a cutoff of -0.50 standard deviation below the mean. Chance-corrected agreement (kappa coefficient) between the two tests was 0.41. We conclude that TIMP items have much in common with those of the AIMS at three months of age and that both tests identify a similar group of infants as having low motor performance. Combined with the fact that the TIMP is sensitive to change with age and is relevant to daily life interactions, these results provide support for the validity of the TIMP as a tool for assessing motor performance in infants.
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