Twin Research

Articles

Zygosity diagnosis in young twins by parental report

MJH Rietvelda1 c1, JC van der Valka2, IL Bongersa3, TM Stroeta4, PE Slagbooma5 and DI Boomsmaa6

a1 Vrije Universiteit, Department of Biological Psychology, Amsterdammjh.rietveld@psy.vu.nl

a2 Vrije Universiteit, Department of Biological Psychology, Amsterdam; Erasmus University, Department of Child and Adolescent Psychiatry, Rotterdam

a3 Vrije Universiteit, Department of Biological Psychology, Amsterdam

a4 Vrije Universiteit, Department of Biological Psychology, Amsterdam

a5 TNO-PG, Gaubius Laboratory, Department of Vascular and Connective Tissue Research, Leiden, The Netherlands

a6 Vrije Universiteit, Department of Biological Psychology, Amsterdam

Abstract

This study reports on zygosity determination in twins of childhood age. Parents responded to questionnaire items dealing with twin similarity in physical characteristics and frequency of mistaking one twin for another by parents, relatives and strangers. The accuracy of zygosity diagnosis was evaluated across twins aged 6, 8, and 10 and across parents. In addition, it was examined whether the use of multiple raters and the use of longitudinal data lead to an improvement of zygosity assignment. Complete data on zygosity questions and on genetic markers or blood profiles were available for 618 twin pairs at the age of 6 years. The method used was predictive discriminant analyses. Agreement between zygosity assigned by the replies to the questions and zygosity determined by DNA markers/blood typing was around 93%. The accuracy of assignment remained constant across age and parents. Analyses of data provided by both parents and collected over multiple ages did not result in better prediction of zygosity. Details on the discriminant function are provided. Twin Research (2000) 3, 134–141.

(Revised February 28 2000)

(Accepted March 24 2000)

Keywords

  • twin zygosity;
  • childhood;
  • questionnaire;
  • review;
  • discriminant analysis

Correspondence:

c1 Correspondence: MJH Rietveld, Vrije Universiteit, Department of Biological Psychology, De Boelelaan 1111, 1081 HV Amsterdam, The Netherlands. Fax: + 31 20 444 8832; Tel: + 31 20 444 8812

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