Ascertainment bias for non-twin relatives in twin proband studies

John P. Rice, Irving I. Gottesman, Brian K. Suarez, Dennis H. Orourke, Theodore Reich

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


When families are ascertained through affected twins, as for example when twin probands are selected from a registry and their non-twin relatives studied, a correction for ascertainment bias is needed. It is shown that probandwise counting (where relatives of doubly ascertained twin pairs are counted twice) is the appropriate method. The bias resulting from pairwise counting is given and depends on the genetic model and on the probability of selecting an affected twin as a proband. For the multifactorial and generalized single major locus models the bias is small, and the problems associated with nonindependent ascertainment are negligible in practice.

Original languageEnglish
Pages (from-to)202-207
Number of pages6
JournalHuman heredity
Issue number3
StatePublished - 1982


  • Ascertainment
  • Proband
  • Probandwise concordance
  • Twin study


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