Discussion
We found only moderate correlations between the AIMS and the PDMS-2 and its subscales in our validity study of the AIMS and the PDMS-2 in Norwegian infants born preterm (gestational age ≤ 32 weeks), except from the correlation between the AIMS and the locomotion subscale of the PDMS-2 which showed good to excellent correlation. This finding is in line with Snyder et al. [In this sample of infants, more infants received a score below average on the AIMS as compared to their scores on the PDMS-2. Previous studies from Belgium [The consistency between the two tests was good as shown by the spread of the scores in the Bland Altman plot, which was evenly distributed with 98% within the limit of agreement at 6 months and within 95% at 12 months. These findings indicate that the two tests can be used interchangeably. However, there seems to be a trend at 12 months, that the difference between the methods get smaller as the average increases.The AIMS as compared to the PDMS-2, both at 6- and at 12- months PTA, was shown to be a slightly better predictor of atypical motor development at 24 months in this group of infants born preterm. Because the AIMS is a shorter, less time-consuming test involving minimal manipulation of infants as compared to the full version of the PDMS-2, the AIMS might be the preferable tool when assessing motor development in infants born preterm at 6- and 12- months PTA. An alternative to the AIMS might be using only the gross motor scale or the locomotion subscale of the PDMS-2, when assessing the infants at 6- or at 12- months, since these were better predictors compared to the full version of the test and can also be performed within the same time as the AIMS.