Evaluating current policy for detecting mosaicism in amniotic fluid cultures: Implications for current cell counting practices

Samuel P. Caudill, Daniel L. Van Dyke, Andrew T.L. Chen, John A. Reidy, Paul S. Ing, Stuart Schwartz, Gail H. Vance

Research output: Contribution to journalArticle

1 Scopus citations


Chromosomal mosaicism is one of the most vexing problems for clinical cytogenetic laboratories and personnel time used for analysis at the microscope is one of the principle costs in cytogenetic laboratories. We use data collected from 26 cytogenetic laboratories to evaluate whether the American College of Medical Genetics guidelines for minimum number of cells to count to exclude mosaicism in amniotic fluid specimens is appropriate. An accurate estimate of the number of mosaics that are missed by current cell counting practices is an important step in this process. Thus, we present a new method for estimating the number of mosaics that are missed and we use computer simulation to evaluate this new method. Our results indicate that if the clinical significance of mosaicism is suspected to be minimal for certain cytogenetic anomalies when the percentage of abnormal cells is 15 per cent or less, then it may be sufficient to use a 15-cell counting-rule-for-detection along with a minimum total cell count of 30 regardless of whether abnormal cells or normal cells are in the minority.

Original languageEnglish (US)
Pages (from-to)615-622
Number of pages8
JournalStatistics in Medicine
Issue number4
StatePublished - Feb 28 2005



  • Binomial distribution
  • Cytogenetics
  • Mosaic heterogeneity
  • Mosaicism

ASJC Scopus subject areas

  • Epidemiology

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