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Large-scale studies

Data Summary

Published Variant
- SNP: 1391
- CNV: 398
- Others: 173
Published Gene: 359
Published Region: 128
Pathway by PBA: 8
Study: 361

Study Report

Basic Info

Reference	Cheuk DK, 2006(a)16917940
Citation	Cheuk D. K., Li S. Y. and Wong V. (2006) "Exon 3 polymorphisms of dopamine D4 receptor (DRD4) gene and attention deficit hyperactivity disorder in Chinese children." Am J Med Genet B Neuropsychiatr Genet, 141B(8): 907-11.
Study Design	case-control and family-based
Study Type	Candidate-gene association study
Sample Size	64 cases and 64 controls
Predominant Ethnicity	Mongoloid
Population	China
Gender	52 boys, 12 girls for cases and controls respectively
Age Group	Children/Adolescents : below 18 years

Detail Info

Summary	They perform a study to investigate the association between ADHD and DRD4 gene polymorphism in Chinese children in Hong Kong. In this prospective family-based and case-control study during January-June 2004, they recruited consecutive Chinese children diagnosed with ADHD by DSM-IV and sex-matched controls admitted for acute upper respiratory infection, excluding those with perinatal brain insults, mental retardation, or neurological deficits. VNTR polymorphisms of the DRD4 gene were determined by standard PCR followed by agarose gel electrophoresis. Sixty-four ADHD cases (52 boys, 12 girls), their family members, and 64 normal controls were recruited. The 4-repeat allele (84.4%) and the 4/4-repeat genotype (70.3%) were the most prevalent. Both family-based and case-control analyses showed no association between ADHD and DRD4 gene polymorphisms. However, the longer repeat alleles had a positive trend association with ADHD in the case-control analysis.
Total Sample	Altogether 64 ADHD cases (52 boys (81.3%), 12 girls (18.7%); M:F=4.3:1) and 64 sex-matched normal controls were recruited.
Sample Collection	Chinese children
Diagnosis Description	The diagnosis of ADHD was made according to the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criteria after a structured interview which incorporated parental and teachers' reports of behavioral symptoms, clinical observation of behaviors, Aberrant Behavioral Checklist, and tests of attention such as the Conners Continuous Performance Test. Forty-three (67.2%) ADHD patients were classified to the combined subtype while 16 (25%) and 5 (7.8%) ADHD patients belonged to the predominantly inattentive and predominantly hyperactive-impulsive subtypes, respectively.
Technique	Three milliliters of blood was taken from the cases and their parents and siblings and the controls for DNA analyses in the pediatric laboratory in The University of Hong Kong. Genomic DNA extraction was performed by traditional salting-out method. Primers used for amplification of VNTR in exon 3 of DRD4 gene were as described by Curran and colleagues [Curran et al., 2001]. More descriptions about laboratory methods could be found in the original publication.
Analysis Method	Family-based allele transmission analysis was performed by the standard transmission dysequilibrium test (TDT). Odds ratios of ADHD for the presence of a particular allele and genotype were determined by comparison between cases and controls and its significance determined by the chi-squared tests. The trend association between the repeat length and ADHD was assessed by the chi-squared test for linear trend.
Result Description	Both family-based and case-control analyses showed no association between ADHD and DRD4 gene polymorphisms (transmission dysequilibrium test (TDT): P-value=0.91 and P-value=0.33 for the 7-repeat and 4-repeat alleles, respectively; OR for the 7-repeat allele=2.01 (95% CI 0.07¨C60.4, P-value=0.66), OR for the 4-repeat allele=1.51 (95% CI 0.80¨C2.85, P-value=0.2)). However, the longer repeat alleles had a positive trend association with ADHD (P-value=0.01) in the casecontrol analysis.

Other variant reported by this study (count: 1)

Variant Name	Allele Change	Risk Allele	Statistical Values	Author Comments	Result of Statistical Analysis
DRD4 exon3 VNTR			2R: P-value=0.07, OR=0.52; TDT P-value=0.65; 4R: P-value=0.2...... 2R: P-value=0.07, OR=0.52; TDT P-value=0.65; 4R: P-value=0.2, OR=1.51; TDT P-value=0.33; 3R/5R/6R: no P-value; 7R: P-value=0.66, OR=2.01; TDT P-value=0.99; More...	not significantly associated with ADHD	Non-significant

Genes reported by this study (count: 1)