Cytogenetic heteromorphisms: survey results and reporting practices of giemsa-band regions that we have pondered for years.
BACKGROUND
Cytogenetic heteromorphisms (normal variants) pose diagnostic dilemmas. Common Giemsa-band heteromorphisms are not described in the literature, although Giemsa-banding is the method most frequently used in cytogenetic laboratories.


OBJECTIVE
To summarize the responses from more than 200 cytogeneticists concerning the definition and reporting of cytogenetic heteromorphisms, to offer these responses as a reference for use in clinical interpretations, and to provide guidance for interpretation of newly defined molecular cytogenetic heteromorphisms.


METHODS
The Cytogenetics Resource Committee of the College of American Pathologists and the American College of Medical Genetics administered a proficiency testing survey in 1997 to 226 participant cytogenetic laboratories. Supplemental questions asked whether participants considered particular Giemsa-banded chromosomal features to be heteromorphisms and if these would be described in a cytogenetic clinical report.


RESULTS
Responses were obtained from 99% of participants; 61% stated they would include selected heteromorphism data in a clinical report. More than 90% considered prominent short arms, large or double satellites, or increased stalk length on acrocentric chromosomes to be heteromorphisms; 24% to 36% stated that they would include these in a clinical report. Heterochromatic regions on chromosomes 1, 9, 16, and Y were considered heteromorphisms by 97% of participants, and 24% indicated they would report these findings. Pericentric inversions of chromosomes 1, 2, 3, 5, 9, 10, 16, and Y were considered heteromorphisms with more than 75% of respondents indicating they would report these findings.


CONCLUSIONS
Responses were not unanimous, but a clear consensus is presented describing which Giemsa-band regions were considered heteromorphisms and which would be reported.
Brothman
Arthur R
AR
Department of Pediatrics and Human Genetics, University of Utah School of Medicine, Salt Lake City, USA. art.brothman@genetics.utah.edu
Schneider
Nancy R
NR
Saikevych
Irene
I
Cooley
Linda D
LD
Butler
Merlin G
MG
Patil
Shivanand
S
Mascarello
James T
JT
Rao
Kathleen W
KW
Dewald
Gordon W
GW
Park
Jonathan P
JP
Persons
Diane L
DL
Wolff
Daynna J
DJ
Vance
Gail H
GH
D001399:Azure Stains; D002869:Chromosome Aberrations / Q000145:classification*; D002871:Chromosome Banding / Q000379:methods* / Q000592:standards*; D003582:Cytogenetics; D006801:Humans; D007753:Laboratories / Q000592:standards*; D011110:Polymorphism, Genetic; D012955:Societies, Medical; D011795:Surveys and Questionnaires; D014481:United States
D001399:Azure Stains