title: Importance of allele frequency estimates in epidemiological studies.
abstract: This study addresses the issue of appropriate allelic frequency estimates in epidemiological studies. Reasons for imprecise estimate of allele frequency may be population stratification, and lack of power of many published studies to define true allele frequencies in the general population. As an example of the lack of power of epidemiological studies, we plot the frequency of GSTM1 deletion versus sample size for the 79 studies from the GSEC pooled analysis. The estimate of allele frequency derived from small groups of controls deviates more from the true frequency than the estimate derived from larger studies. We discuss the possible consequences of not properly defining allele frequencies in the population. This may reflect on the conduct of association studies, on assessment of the effects of multigenic mechanisms, and on the determination of genetic diversity.
authors.affiliation: Molecular and Genetic Epidemiology Unit, Padiglione Marangoni, Ospedale Policlinico IRCCS, Via F. Sforza 35, 20122 Milan, Italy. taioli@policlinico.mi.it
authors.forename: Emanuela
authors.initials: E
authors.lastname: Taioli
authors.forename: Paola
authors.initials: P
authors.lastname: Pedotti
authors.forename: Seymour
authors.initials: S
authors.lastname: Garte
mesh_terms: D016021:Epidemiologic Studies; D005787:Gene Frequency / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D005982:Glutathione Transferase / Q000235:genetics*; D006801:Humans; D005810:Multigene Family; D011110:Polymorphism, Genetic / Q000235:genetics*
chemical_list: D005982:Glutathione Transferase