However, this could not be checked as families not enrolled were not recorded. The child��s grandparents�� countries of birth were recorded to provide an acceptable proxy for ethnicity. Buccal swabs from the mother and child were taken into transport/lysis buffer and kept at ambient temperatures during postage to the laboratory in Cambridge. Plasma or serum samples stored at 220uC were shipped frozen to Cambridge. A total of 457 mother-child pairs met the inclusion criteria to participate in the study, which included successful preparation of DNA. For the North American study sample, family-based allelic association tests based on the TDT but generalised to allow analysis under additive and dominant models of inheritance were performed within FBAT. Allelic associations, and relative risk estimates, were obtained by creating a case/pseudocontrol study where the cases comprise the genotypes of the affected offspring, and the pseudo-sib controls are the one to three other genotypes which the affected offspring might have received from the parents. The relative risks were estimated using conditional logistic regression analysis, with test statistic, OR, 95% CI and P values used to evaluate significance of an association. A stepwise conditional logistic-regression Amikacin hydrate procedure was used to evaluate the relative importance of variants within and between candidate gene loci, as before. Since there was a priori clinical evidence to support candidacy of each of the genes studied, and not all markers within genes were independent, we did not apply a multiple testing correction. However, the stepwise logistic regression analyses permitted us to determine whether markers within each gene showed independent main effects. To obtain statistical evidence for imprinting, we used a loglinear method designed to evaluate parent-of-origin effects in caseparent trios once mother��s and child��s genotypes have been included in the model. We used the program LEM which also allows assessment of Albaspidin-AA maternal genotype effects with or without including a parent-of-origin effect. For the European cohort, where only mother-child pairs were available, the same parameterization was employed and the models were fitted using an inhouse program written by Dr Heather Cordell, under the assumption of random mating and Hardy Weinberg equilibrium using public domain allele frequencies for European populations.