Assessment of the carotid artery by MRI at 3T: a study on reproducibility

PURPOSE: To examine the reproducibility of carotid artery dimension measurements using 3T MRI. MATERIALS AND METHODS: Ten healthy volunteers underwent three scans on two occasions for assessment of total vessel wall area (TVWA), total luminal area (TLA), and minimum (MinT) and maximum (MaxT) vessel wall thickness. A double inversion-recovery (IR) fast gradient-echo (FGRE) sequence was used on a commercial 3T system. During the first visit the subjects were scanned twice. The third scan was performed at least four days later. One observer traced all scans, and a second observer retraced the first scan series. RESULTS: For TVWA an interclass correlation (ICC) of 0.994 was calculated with all three scans taken into account. The interobserver ICC was 0.984. The agreement between the scans for TLA showed an ICC of 0.982 with an interobserver ICC of 0.998. For MinT and MaxT an ICC of 0.843 and 0.935 were calculated, with interobserver ICCs of 0.860 and 0.726, respectively. CONCLUSION: With the use of a commercial 3T MR system, TVWA, TLA, and wall thickness measurements of the carotid artery can be assessed with good reproducibility.     

Genetic meta‐analysis of obsessive–compulsive disorder and self‐report compulsive symptoms

We investigated whether obsessive–compulsive (OC) symptoms from a population‐based sample could be analyzed to detect genetic variants influencing obsessive–compulsive disorder (OCD). We performed a genome‐wide association studies (GWAS) on the obsession (rumination and impulsions) and compulsion (checking, washing, and ordering/precision) subscales of an abbreviated version of the Padua Inventory (N = 8,267 with genome‐wide genotyping and phenotyping). The compulsion subscale showed a substantial and significant positive genetic correlation with an OCD case–control GWAS (r _G = 0.61, p = .017) previously published by the Psychiatric Genomics Consortium (PGC‐OCD). The obsession subscale and the total Padua score showed no significant genetic correlations (r _G = ?0.02 and r _G = 0.42, respectively). A meta‐analysis of the compulsive symptoms GWAS with the PGC‐OCD revealed no genome‐wide significant Single‐Nucleotide Polymorphisms (SNPs combined N = 17,992, indicating that the power is still low for individual SNP effects). A gene‐based association analysis, however, yielded two novel genes (WDR7 and ADCK1). The top 250 genes in the gene‐based test also showed a significant increase in enrichment for psychiatric and brain‐expressed genes. S‐Predixcan testing showed that for genes expressed in hippocampus, amygdala, and caudate nucleus significance increased in the meta‐analysis with compulsive symptoms compared to the original PGC‐OCD GWAS. Thus, the inclusion of dimensional symptom data in genome‐wide association on clinical case–control GWAS of OCD may be useful to find genes for OCD if the data are based on quantitative indices of compulsive behavior. SNP‐level power increases were limited, but aggregate, gene‐level analyses showed increased enrichment for brain‐expressed genes related to psychiatric disorders, and increased association with gene expression in brain tissues with known emotional, reward processing, memory, and fear‐formation functions.     

ADHD in Dutch adults: Heritability and linkage study

Attention deficit/hyperactivity disorder (ADHD) is a neurodevelopmental phenotype that persists into adulthood. This study investigated the heritability of inattentive and hyperactive symptoms and of total ADHD symptomatology load (ADHD index) in adults and performed linkage scans for these dimensions. Data on sibling pairs and their family members from the Netherlands Twin Register with genotype and phenotype data for inattention, hyperactivity and ADHD index (～750 sib‐pairs) were analyzed. Phenotypes were assessed with the short self‐report form of the Conners' Adult ADHD Rating Scales (CAARS). Heritabilities were estimated in SOLAR under polygenic models. Genome‐wide linkage scans were performed using variance components (VC) in MERLIN and MINX and model‐based linkage analysis was carried out in MENDEL with empirical evaluation of the results via simulations. Heritability estimates for inattention, hyperactivity and ADHD index were 35%, 23%, and 31%, respectively. Chromosomes 18q21.31–18q21.32 (VC LOD = 4.58, p_emp = 0.0026) and 2p25.1 (LOD = 3.58, p_emp = 0.0372) provided significant evidence for linkage for inattention and the ADHD index, respectively. The QTL on chromosome 2p25.1 also showed suggestive linkage for hyperactivity. Two additional suggestive QTLs for hyperactivity and the ADHD index shared the same location on chromosome 3p24.3–3p24.1. Finally, a suggestive QTL on 8p23.3–8p23.2 for hyperactivity was also found. Heritability of inattention, hyperactivity and total ADHD symptoms is lower in adults than in children. Chromosomes 18q and 2p are likely to harbor genes that influence several aspects of adult ADHD. © 2011 Wiley‐Liss, Inc.