Boyle M H, Offord D R, Racine Y A, Catlin G
Department of Psychiatry, McMaster University, Hamilton, Ontario, Canada.
J Am Acad Child Adolesc Psychiatry. 1991 May;30(3):449-56. doi: 10.1097/00004583-199105000-00016.
This article presents an analysis of sample loss in a 4-year follow-up of children aged 4 to 12 who participated in the Ontario Child Health Study in 1983. Of the 1,617 children participating in the original Ontario Child Health Study, 1,172 (72.5%) were located and enlisted at follow-up in 1987. Based on wave-one assessments, nonparticipants at follow-up tended to have higher levels of psychopathology and family risk variables. Respondents were matched with nonparticipants and differentially weighted to compensate for selective loss. In comparing estimates based on actual (observed) and weighted responses in the follow-up sample, it was found that the effects of sample loss depended on the analytical focus. Evaluations of outcome of disorder and risk for disorder were not affected by sample loss. Evaluation of variables that predict persistence of disorder (prognosis) was affected by a bias toward the null.
本文对1983年参与安大略儿童健康研究的4至12岁儿童进行了为期4年的随访，并分析了样本流失情况。在最初参与安大略儿童健康研究的1617名儿童中，1172名（72.5%）在1987年随访时被找到并重新登记。根据第一波评估，随访时未参与者往往具有较高水平的精神病理学和家庭风险变量。将受访者与未参与者进行匹配，并采用不同的加权方法以补偿选择性流失。在比较基于随访样本中实际（观察到的）和加权回复的估计值时，发现样本流失的影响取决于分析重点。对疾病结局和疾病风险的评估不受样本流失影响。对预测疾病持续性（预后）的变量评估受到偏向零假设的偏差影响。
