Research Findings

Methods Studies - Biological Samples

Relationship between plasma 25-hydroxymitamin D and leucocyte telomere length by sex and race in a US study (2016)
 Among 1,154 U.S. radiologic technologists Vitamin D concentration was not associated with long leukocyte telomere length (LTL) in white females, white males, black females, or black males; however, Vitamin D deficiency was associated with short LTL in whites but not blacks.
Sunlight and other determinants of circulating 25-Hydroxyvitamin D levels in black and white participants of a nationwide U.S. study (2013)
 Levels of circulating 25-hydroxyvitamin D (25(OH)D) (vitamin D) were assessed in blood samples from 1,500 radiologic technologists. Age and vitamin D supplement use were associated with circulating vitamin D levels in both whites and blacks, while body mass index, certain seasons of blood draw, and number of hours spent outdoors being physically active were related to vitamin D level in whites only.
Variability and reproducibility of circulating vitamin D in a nationwide U.S. population (2013)
 The variability and reproducibility of circulating vitamin D levels were evaluated in blood samples taken from 528 male and female U.S. radiologic technologists at two different times during a single year. Findings suggested that a single blood sample obtained in spring or fall provided a reasonable average vitamin D measurement over a one-year period.
The impact of delayed blood centrifuging, choice of collection tube, and type of assay on 25-hydroxyvitamin D concentrations (2010)
 25-hydroxyvitamin D concentrations were assessed in 20 healthy volunteers using two different assays (RIA and CLIA/LIAISON), three different collection tubes (red top serum, plasma heparin, and plasma EDTA), and at four different centrifuging times (2, 24, 72, and 96 hours after blood draw). 25(OH)D concentrations did not differ according to type of assay or centrifuge time post-blood draw. Concentrations were somewhat higher for heparin tubes, especially with the CLIA/LIAISON assay, but only for samples centrifuged 96 hours after blood draw. Researchers concluded that it was not necessary to require a specific type of assay, collection tube, or immediate centrifuging.
Blood spots as an alternative to whole blood collection and the effect of a small monetary incentive to increase participation in genetic association studies (2009)
 We conducted a study to evaluate whether offering blood spot collection as an alternative to venipuncture blood collection, with or without a small monetary incentive, would increase participation in genetic epidemiologic studies. Among female radiologic technologists who previously declined to provide a venipuncture sample for a breast cancer case-control study, 37% of cases and 28% of controls provided a died blood spot card. The $2.00 bill incentive significantly improved participation among controls but was not associated with response among cases. We concluded that collection of dried blood spot cards in addition to venipuncture blood samples may be a feasible method to increase participation in genetic case-control studies.
No evidence for differences in DNA damage assessed before and after a cancer diagnosis (2008)
 To assess whether cancer diagnosis is associated with functional deficits in DNA repair, we used the alkaline comet assay to quantify DNA damage in lymphoblastoid cells collected before and after cancer diagnosis in 26 individuals. We found no significant differences in the before and after diagnosis mean comet values. This finding is important because it suggests that bias from using post-diagnostic samples instead of pre-diagnostic samples may be minimal.
Candidate single nucleotide polymorphism selection using publicly available tools: a guide for epidemiologists (2006)
 Single nucleotide polymorphisms are the most common form of human genetic variation, with millions present in the human genome. Because only 1% might be expected to confer more than modest individual effects in association studies, the selection of predictive candidate variants for complex disease analyses is formidable. We developed a semi-quantitative relative ranking strategy for selecting candidate variants, and describe in this paper a "real world" application of existing bioinformatics tools for use in large epidemiologic studies and genetic analyses.
Genetic variation and willingness to participate in epidemiologic research: data from three studies (2005)
 We examined single nucleotide polymorphism genotypes, haplotypes, and short tandem repeats among control groups from three studies with different recruitment designs that included early, late, and never questionnaire responders, one or more participation incentives, and blood or buccal cell collection. We found little evidence to suggest that genotype differences underlie response characteristics in molecular epidemiologic studies, although a greater variety of genes should be examined.