Factors affecting maternal participation in the genetic component of the National Birth Defects Prevention Study—United States, 1997–2007

Abstract

Purpose As epidemiological studies expand to examine gene–environment interaction effects, it is important to identify factors associated with participation in genetic studies. The National Birth Defects Prevention Study is a multisite case–control study designed to investigate environmental and genetic risk factors for major birth defects. The National Birth Defects Prevention Study includes maternal telephone interviews and mailed buccal cell self-collection kits. Because subjects can participate in the interview, independent of buccal cell collection, detailed analysis of factors associated with participation in buccal cell collection was possible. Methods Multivariable logistic regression models were used to identify the factors associated with participation in the genetic component of the study. Results Buccal cell participation rates varied by race/ethnicity (non-Hispanic whites, 66.9%; Hispanics, 60.4%; and non-Hispanic blacks, 47.3%) and study site (50.2–74.2%). Additional monetary incentive following return of buccal cell kit and shorter interval between infant’s estimated date of delivery and interview were associated with increased participation across all racial/ethnic groups. Higher education and delivering an infant with a birth defect were associated with increased participation among non-Hispanic whites and Hispanics. Conclusion Factors associated with participation varied by race/ethnicity. Improved understanding of factors associated with participation may facilitate strategies to increase participation, thereby improving generalizability of study findings.

The national birth defects prevention study: A review of the methods

“…Glidewell and colleagues (Glidewell and others, 2013) examined factors associated with participation in buccal cell collection in the NBDPS. Buccal responders were more likely to be non-Hispanic white, older case mothers with higher education, higher household incomes, pregnancies that were intended, to have had a shorter interval between their EDD and interview date, to have received a redesigned buccal cell collection kit and an additional $20 incentive, to have consumed folic acid and not to have smoked cigarettes during the periconceptional period.…”

Impact of sample collection participation on the validity of estimated measures of association in the National Birth Defects Prevention Study when assessing gene‐environment interactions

“…To expand our findings to gene-environment interactions assumes that there is limited genetic heterogeneity between sample collectors and noncollectors. Although we know from previous studies (Crider et al, 2006; Glidewell et al, 2014; McQuillan, Porter, Agelli, & Kington, 2003; Moorman et al, 2004) that race and ethnicity are factors that consistently affect whether a participant collects and submits specimens, genetic studies typically stratify data by race and ethnicity to account for genetic heterogeneity during analyses. Other factors observed to affect collection of specimens for genetic research, such as age, income, and education, should have limited genetic heterogeneity between sample collectors and noncollectors.…”

“…It has a population-based, multi-state ascertainment that included participants who were representative of their base populations (Cogswell et al, 2009), specimen collection quantity and quality that improved over time (Gallagher et al, 2011), and clinicians who reviewed each case using standard definitions (Rasmussen et al, 2003). After establishing that nonresponse in buccal cell collection and submission was not a random event (Glidewell et al, 2014), there were some concerns over how representative risk estimates limited to sample collectors would be. This study allays concerns by showing that the majority of estimates for sample collectors and noncollectors are comparable, providing some reassurance as gene-environment interactions are assessed using NBDPS samples and interview data.…”

“…In addition to decreased power that results from suboptimal participation rates, there is concern about self-selection bias given the documented differences in submitting buccal cell samples based on demographic, lifestyle, or other factors (Crider, Reefhuis, Woomert, & Honein, 2006; Glidewell et al, 2014). …”

Maternal exposures in the National Birth Defects Prevention Study: Time trends of selected exposures

“…Maternal race/ethnicity was selected and assessed because it is strongly associated with study site and might have been impacted by changes in the study sites and because it might be associated with other exposures of interest (Siega-Riz et al, 2009, Ma et al, 2010, Glidewell et al, 2014). Obesity was selected because it is one of the strongest and most consistent risk factors for many major birth defects, and obesity prevalence in the United States has increased over the time period of the study (Waller et al, 2007, Stothard et al, 2009, Flegal et al, 2012).…”