Comparison of recruitment, retention, and compliance results for three children's exposure monitoring studies

The School Health Initiative: Environment, Learning, Disease (SHIELD) study, the Minnesota Children's Pesticide Exposure Study (MNCPES), and the National Cooperative Inner-City Asthma Study(NCICAS) are three of the most intensive and invasive exposure-monitoring projects ever undertaken in children. An intrinsic facet of each study was the need to recruit children and their families, retain them for the duration of the project, and ensure that they completed monitoring protocols successfully. All of the studies used fiscal incentives to encourage participation, retention, and compliance. Recruitment rates varied from 40% in MNCPES, to 57% in SHIELD, to 64% in NCICAS, while retention rates varied from 85% in SHIELD, to 94% in MNCPES, to 95% in NCICAS. Rates of compliance with exposure sampling procedures were typically > 80% for each study. For example, >= 85% of the enrolled children provided all requested urine samples (1 for NCICAS, 2 for SHIELD, 3 for MNCPES), and 82% of the children in SHIELD provided two out of two blood samples (optional in MNCPES and NCICAS). However, compliance rates were substantially lower (34% SHIELD, 40% NCICAS, not applicable to MNCPES) for the more complex and time-consuming protocol used to collect peak flow data. Overall, results demonstrate that it is practical and affordable to conduct demanding exposure-monitoring studies in children, including children from poor minority communities.