Kim Annink

98 Chapter 5     Kinderintelligentie Test (RAKIT; Amsterdam Child Intelligence Test Revised) (24). 4. Intelligence Quotient (IQ): the Intelligence Scale for Children, WISC-III-NL (25). Statistical analyses To detect the differences in baseline characteristics One-Way ANOVA and χ2 tests were performed. The ANOVA test with Bonferroni post-hoc test, or the Kruskal-Wallis-H test with post-hoc test when appropriate, was used to compare hippocampal volumes, memory and IQ between the groups. We tested asymmetry in hippocampal volumes with a paired samples t-test. Multivariable linear regression was performed to determine the association between HIE, age, sex and hippocampal volumes. Further, we performed univariate and multivariable linear regression analyses to estimate the association between hippocampal volumes and memory and IQ. The percentage hippocampus/ICV, group, age, sex, socioeconomic status based on educational level of the mother (SES) and interaction terms were initially included in the multivariable model. Interaction terms were included to determine whether the effect of hippocampal volume on memory and IQ differed between boys/girls, controls/HIE1/HIE2, SES categories and/or different ages. P-values >0.1 were used to remove and p-values <0.05 to enter the predictors stepwise and bidirectionally in the model. For multivariable linear regression we combined SES categories to limit the number of predictors (Table 1). Statistical analysis was performed using SPSS version 21, and R version 3.1.2. P-values <0.05 were considered statistically significant. All p-values were corrected for multiple comparisons using the Bonferroni correction. RESULTS Study population In total, 164 full-term infants with HIE were admitted to the Neonatal Intensive Care Unit of the Wilhelmina Children’s hospital in Utrecht between 1993 and 1997. In the neonatal period 46 children died, including all children with severe HIE. Of the 118 survivors, 81 were examined at 9 to 10 years of age. Of the children not examined, six were too severely affected to participate, seven could not be traced (HIE1: n=5, HIE2: n=2) and the parents of 24 children (HIE1: n=13, HIE2: n=11) refused to participate, mainly because MRI was part of the protocol. Fifty-three controls were included. An MRI was obtained and was of sufficient quality for volumetric analysis in 26 of the 34 HIE1 infants, 27 of the 47 HIE2 infants and 37 of the 53 controls. In the other