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Optimization of Zygosity Determination by Questionnaire and DNA Genotyping in Chinese Adolescent Twins

Published online by Cambridge University Press:  21 February 2012

Jie Chen
Affiliation:
Key Lab of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China.
Xinying Li*
Affiliation:
Key Lab of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China. [email protected]
Zhiyan Chen
Affiliation:
Key Lab of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China.
Xiaodong Yang
Affiliation:
Key Lab of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China.
Jie Zhang
Affiliation:
Key Lab of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China.
Qing Duan
Affiliation:
Key Lab of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China.
Xiaojia Ge
Affiliation:
Key Lab of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China; Institute of Child Development, University of Minnesota Twin Cities, Minneapolis 55455, United States of America.
*
*Address for correspondence: Xinying Li, Address: D303, A4 Da-tun Road, Chaoyang District, Beijing, 100101, China.

Abstract

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The main aim of this study was to develop and optimize a questionnaire-based zygosity determination method in Chinese adolescent twins. Participants were 471 pairs of same-sex twins (345 monozygotic, 126 dizygotic) with a mean age of 14.56 years (SD = 2.62). A second sample was recruited for cross-validation, including 382 pairs of same-sex twins (261 monozygotic, 121 dizygotic) with a mean age of 12.53 years (SD = 2.22). The questionnaire consisted of 12 questions dealing with co-twin similarity or frequency of confusion. Two means were put forward to improve the predictive accuracy of the questionnaire — adding parent-reports to the analysis, and using a 2-point rather than 3-point response format. DNA genotyping was performed on nine short tandem repeat loci, with an estimated zygosity classification accuracy very close to 100%. The validity of all questionnaires was assessed by being compared to the results of DNA analysis. Results of stepwise logistic regression analysis showed that the predictive accuracy of the 3-point self-reported questionnaire is 83.8%. Using parent-reports and 2-point scale led to 3.9% and 4.6% increase in predictive accuracy, respectively. When using the parent-reports and children's self-reports jointly, the predictive accuracy was enhanced to 90.6%. For the cross-validation, the equations and cut-offs derived from the first sample led to an acceptable accuracy (91.3%) in the second sample. In conclusion, the method we developed can be used in future studies among Chinese adolescent twins. Multiple-rater and 2-point response format were suggested for all twin studies for enhancing the predictive accuracy of questionnaires.

Type
Articles
Copyright
Copyright © Cambridge University Press 2010