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Age- and Sex-differences in the Validity of Questionnaire-based Zygosity in Twins

  • Lene Christiansen (a1), Henrik Frederiksen (a2), Karoline Schousboe (a3), Axel Skytthe (a4), Nicole von Wurmb-Schwark (a5), Kaare Christensen (a6) and Kirsten Kyvik (a7)...

Questionnaire-based zygosity assessment in twins has generally been found to be valid. In this report we evaluate sex- and age-differences in the validity of such questionnairebased classification when using the four questions that have been the basis of zygosity assessment in The Danish Twin Registry for half a century. Three hundred and forty-two male and 531 female twin pairs were zygosity diagnosed using genetic markers and the results compared with the original questionnaire based classification. We found significant differences in the accuracy of questionnaire based zygosity diagnosis when stratifying the data for sex as well as age: males and monozygotic having the highest misclassification. However, even in the group with the highest misclassification rate the frequency was less than 8%. The overall misclassification rate was only 4%, with a clear tendency towards a higher proportion of misclassified monozygotic than dizygotic twins. The results demonstrate that questionnaire based zygosity diagnosis can still be regarded as a valid and valuable classification method for most purposes.

Corresponding author
*Address for correspondence: Lene Christiansen, MSc, Ph.D., The Danish Twin Registry, Epidemiology, Institute of Public Health, University of Southern Denmark, Sdr. Boulevard 23A, DK-5000 Odense C, Denmark.
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Twin Research and Human Genetics
  • ISSN: 1832-4274
  • EISSN: 1839-2628
  • URL: /core/journals/twin-research-and-human-genetics
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