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Is attrition bias a problem in neonatal follow-up?

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Author: Hille, E.T.M. · Ouden, A.L. den · Stuifbergen, M.C. · Verrips, G.H.W. · Vogels, A.G.C. · Brand, R. · Gravenhorst, J.B. · Verloove-Vanhorick, S.P.
Institution: TNO Kwaliteit van Leven
Source:Early Human Development, 11, 81, 901-908
Identifier: 238797
doi: doi:10.1016/j.earlhumdev.2005.07.006
Keywords: Health · Attrition bias · Very low birth-weight infants · Very preterm infants · Academic achievement · Controlled study · Disability · Logistic regression analysis · Low birth weight · Newborn · Prematurity · Small for date infant · Adolescent · Child · Child, Preschool · Female · Follow-Up Studies · Humans · Infant, Newborn · Infant, Premature · Male · Netherlands · Premature Birth · Selection Bias


Aim: To assess whether attrition rate influences outcome in the follow-up of very preterm infants. Study design: In a national follow-up study of infants born alive in 1983 in the Netherlands with a gestational age less than 32 weeks and/or a birth weight less than 1500 g, outcome was assessed separately for adolescents who responded early or late to a follow-up invitation at age 14 years. Neonatal data and outcome results of earlier assessments from early and late responders were compared to those of non-responders by univariate and nominal (polytomous logistic) regression analysis. Subjects: There were 723 (76%) early responders, 130 (14%) late responders and 109 (11%) non-responders. Results: We found significantly more non-Dutch origin and more disabilities and school problems at age 10 years in late- and especially in non-responders. At age 14 years, the health utility index was significantly lower in late responders compared to early responders. School outcome did not show difference in relation to the response groups. Conclusion: The results suggest that the incidence of adverse outcome in very preterm infants is underestimated when follow-up is incomplete and hence response rate is not a negligible problem in the assessment of late outcome. Therefore, follow-up studies should include a drop-out analysis to enable comparison to other studies.