Does the requirement of getting active consent from parents in school-based research result in a biased sample? An empirical study.

Active parental consent is a requirement that may threaten the validity of including minors in research. This study investigated possible sources of bias between the responses of children whose parents actively consented to their participation in a school-based survey and those of children whose parents were nonresponders. Due to a serious administrative error in a study to examine health-related quality of life (HRQoL), all 514 eligible schoolchildren were tested, although only 177 parents signed consent. After deliberation, the relevant human research ethics committee gave permission to include all results in the analysis. The HRQoL was not different between the groups. Male children returned significantly fewer consent forms (p=.026). More of the nonresponding group reported that their parents "Never had enough time for them" (p=.023). The high nonresponse rate and associations between response and parental interest and gender indicate that some bias may be introduced through the need for active consent, but overall there were no differences in responses to the quality of life questionnaire.