title: Evaluating current policy for detecting mosaicism in amniotic fluid cultures: implications for current cell counting practices.
abstract: 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.
authors.affiliation: Centers for Disease Control and Prevention, Clinical Chemistry Branch, Atlanta, GA 30341-3724, USA. spcl@cdc.gov
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Caudill
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Van Dyke
authors.forename: Andrew T L
authors.initials: AT
authors.lastname: Chen
authors.forename: John A
authors.initials: JA
authors.lastname: Reidy
authors.forename: Paul S
authors.initials: PS
authors.lastname: Ing
authors.forename: Stuart
authors.initials: S
authors.lastname: Schwartz
authors.forename: Gail H
authors.initials: GH
authors.lastname: Vance
mesh_terms: D000653:Amniotic Fluid / Q000166:cytology*; D016010:Binomial Distribution; D003198:Computer Simulation; D003584:Cytological Techniques / Q000592:standards*; D005260:Female; D006801:Humans; D009030:Mosaicism; D011247:Pregnancy