Biomedical subjects

Cynthia W Garvan

Publications and source records attributed to Cynthia W Garvan.

5 recordsLinked to original sources

PubMed2006

A framework to monitor environment-induced major genes for developmental trajectories: implication for a prenatal cocaine exposure study.

Whether there are specific genes involved in response to different environmental agents and how such genes regulate developmental trajectories during lifetime are of fundamental importance in health, clinical and pharmaceutical research. In this article, we present a novel statistical model for monitoring environment-induced genes of major effects on longitudinal outcomes of a trait. This model is derived within the maximum likelihood framework, incorporated by mathematical aspects of growth and developmental processes. A typical structural model is implemented to approximate time-dependent covariance matrices for the longitudinal trait. This model allows for a number of biologically meaningful hypothesis tests regarding the effects of major genes on overall growth trajectories or particular stages of development. It can be used to test whether and how major genetic effects are expressed differently under altered environmental agents. In a well-designed case-control study, our model has been employed to detect cocaine-dependent genes that affect growth trajectories for head circumference during childhood. The detected gene triggers significant effects on growth curves in both cocaine-exposed (case) and unexposed groups (control), but with different extents. Significant genotype-environment interactions due to this so-called environment-sensitive gene are promising for further studies toward its genomic mapping using polymorphic molecular markers.

Adult↗

PubMed2005

A general model for detecting genetic determinants underlying longitudinal traits with unequally spaced measurements and nonstationary covariance structure.

A mixture model for determining quantitative trait loci (QTL) affecting growth trajectories has been proposed in the literature. In this article, we extend this model to a more general situation in which longitudinal traits for each subject are measured at unequally spaced time intervals, different subjects have different measurement patterns, and the residual correlation within subjects is nonstationary. We derive an EM-simplex hybrid algorithm to estimate the allele frequencies, Hardy-Weinberg disequilibrium, and linkage disequilibrium between QTL in the original population and parameters contained in the growth equation and in the covariance structure. A worked example of head circumference growth in 145 children is used to validate our extended model. A simulation study is performed to examine the statistical properties of the parameter estimation obtained from this example. Finally, we discuss the implications and extensions of our model for detecting QTL that affect growth trajectories.

Algorithms↗

PubMed2004

Proportions, odds, and risk.

Perhaps the most common and familiar way that the results of medical research and epidemiologic investigations are summarized is in a table of counts. Numbers of subjects with and without the outcome of interest are listed for each treatment or risk factor group. By using the study sample data thus tabulated, investigators quantify the association between treatment or risk factor and outcome. Three simple statistical calculations are used for this purpose: difference in proportions, relative risk, and odds ratio. The appropriate use of these statistics to estimate the association between treatment or risk factor and outcome in the relevant population depends on the design of the research. Herein, the enumeration of proportions, odds ratios, and risks and the relationships between them are demonstrated, along with guidelines for use and interpretation of these statistics appropriate to the type of study that gives rise to the data.

Case-Control Studies↗

PubMedDate not supplied

Exploring help-seeking for ADHD symptoms: a mixed-methods approach.

OBJECTIVE: Gender and race differences in treatment rates for attention-deficit/hyperactivity disorder (ADHD) are well documented but poorly understood. Using a mixed-methods approach, this study examines parental help-seeking steps for elementary school students at high risk for ADHD. METHODS: Parents of 259 students (male/female, African American/Caucasian) identified as being at high risk for ADHD completed diagnostic interviews and provided detailed accounts of help-seeking activities since they first became concerned about their child. Help-seeking steps (n=1,590) were analyzed using two methods: inductive analysis based on grounded theory, and deductive quantitative analysis of coded data derived from application of the network-episode model, merged subsequently with demographic and other characteristics. RESULTS: The inductive analysis revealed unique parental perceptions of their children's sick role and of the agents of identification and intervention for each of the four groups. Deductive analysis showed significant variations by race and gender in consultation experiences, in the person or entity being consulted and in the transactions occurring in the consultation, and in illness careers. CONCLUSION: ADHD symptoms are interpreted as having different implications for the sick role and the intervention, dependent on a child's gender and race. Educational interventions need to address cultural stereotypes contributing to inequitable access to treatment.

Attention Deficit Disorder with Hyperactivity↗

PubMedDate not supplied

One size still does not fit all in specific learning disability assessment across ethnic groups.

The use of IQ scores and discrepancy formulas for identifying specific learning disabilities (SLD) has been widely discredited by prominent researchers for more than a decade. Nevertheless, the overwhelming majority of state policies still specify the use of discrepancy formulas, including the simple difference method, which is psychometrically inferior to regression-based methods. This study compares the use of a minimum IQ cutoff score and a simple difference method versus a regression-based method for identifying SLD in a sample of African American and European American full-time college students (N = 117). Replicating the findings from previous studies using typically achieving children, typically achieving adults, and school-age children with SLD, this study adds to the chorus of voices criticizing the use of outdated assessment practices that can have deleterious effects for individuals with SLD. The implications for legislative policy are discussed in the context of the historical overrepresentation of African Americans in all special education categories except SLD and the increased access to higher education that students with SLD have gained during the past decade.

Adolescent↗