Blood Collection, Processing Methods and Maternal Char-acteristics and the Potential Impact on Study Results in a Longitudinal Birth Cohort Study

Abstract

RATIONALE: Blood processing factors and maternal and infant characteristics may influence the cell yield or pattern of cytokine secretion by umbilical cord blood cells.METHODS: Cord blood samples were analyzed on 287 subjects as part of the Childhood Origins of ASThma project (COAST), a prospective study of children at high risk for developing asthma/allergies. Mononuclear cells from samples were separated by centrifugation, counted and stimulated with the mitogen PHA and a suspension of killed staphylococcus, and IFN-γ, IL-10 and IL-13 were quantitated by ELISA. Cell yield and cytokine production were then related to processing factors including method of collection, time between sample collection and preparation, changes in responses over time; as well as maternal and infant characteristics or exposures.RESULTS: Clots in the cord blood samples were associated with a reduction in median cell yield (21% reduction, p < 0.0001), and changes in cytokine secretion, including an 8% reduction in PHA-induced IL-10 (p = 0.004). In addition, season of collection affected total cell yield (p=0.004), with highest median yields in fall and lowest in summer, (difference of 22%). PHA-induced IL-13 responses were also sensitive to season of collection (p=0.002); and were higher in the spring (23% increase) and summer (27% increase) relative to fall or winter. No other variables had significant (p<0.01) effects in multivariate regression models.CONCLUSIONS: Careful documentation of processing and environmental variables is important when collecting cord blood samples. This data does suggest that maternal seasonal exposure affects cord blood response in the baby. RATIONALE: Blood processing factors and maternal and infant characteristics may influence the cell yield or pattern of cytokine secretion by umbilical cord blood cells. METHODS: Cord blood samples were analyzed on 287 subjects as part of the Childhood Origins of ASThma project (COAST), a prospective study of children at high risk for developing asthma/allergies. Mononuclear cells from samples were separated by centrifugation, counted and stimulated with the mitogen PHA and a suspension of killed staphylococcus, and IFN-γ, IL-10 and IL-13 were quantitated by ELISA. Cell yield and cytokine production were then related to processing factors including method of collection, time between sample collection and preparation, changes in responses over time; as well as maternal and infant characteristics or exposures. RESULTS: Clots in the cord blood samples were associated with a reduction in median cell yield (21% reduction, p < 0.0001), and changes in cytokine secretion, including an 8% reduction in PHA-induced IL-10 (p = 0.004). In addition, season of collection affected total cell yield (p=0.004), with highest median yields in fall and lowest in summer, (difference of 22%). PHA-induced IL-13 responses were also sensitive to season of collection (p=0.002); and were higher in the spring (23% increase) and summer (27% increase) relative to fall or winter. No other variables had significant (p<0.01) effects in multivariate regression models. CONCLUSIONS: Careful documentation of processing and environmental variables is important when collecting cord blood samples. This data does suggest that maternal seasonal exposure affects cord blood response in the baby.