Guidelines for G-banding Analysis

· Analysis definition:

· Full band-to-band analysis of all chromosomes in the metaphase, at the microscope

· Karyotyped metaphases may include one or more analyzed metaphases

· Amniotic fluid:

· TAT 14 days

· Flask method:

· 15 mets from 2 or more independent cultures

· Analyze 5 mets

· Karyotype 2 mets

· In-situ method:

· 10 mets, each from a different colony, from 2 or more independent cultures

· Analyze 5 mets

· Karyotype 2 mets

· CVS:

· TAT 14 days

· 20 mets from 2 or more independent cultures

· Analyze 5 mets

· Karyotype 2 mets

· Fetal blood:

· TAT 7 days

· Minimum analyzed / karyotyped as per constitutional blood

· Constitutional studies:

· TAT:

· Lymphocytes: 3 weeks

· Newborn / infant bloods: 3 day preliminary result

· Fibroblasts: 4 weeks

· 10 mets (from 2 independent primary cultures for tissues (fibroblasts)

· Analyze 3 mets

· Karyotype 2 mets

· 550 bands or greater is a reasonable expectation

· Recognized to not always be achievable

· Suspected mosaicism:

· 25 to 50 mets (count)

· Oncology:

· TAT:

· Stat: 3-5 days

· Routine, at diagnosis: 2 weeks (mean)

· Routine, at follow-up: 3 weeks (mean)

· 20 mets if normal

· 25 mets if post-treatment monitoring for original abnormal clone

· If abnormal:

· Enough mets to confirm the presence of an abnormal clone

· If disease transformation is suspected, examine additional mets

· 20 mets if clonal evolution is significant

· Karyotype 1 met per stemline and significant sideline

· 1 Normal metaphase should be at least printed, recommend karyotype

· Culture time:

· BM:

· 24-48 h culture

· Direct maybe

· Blood:

· 24-48 h culture (unstimulated)

· Effusion / fluid:

· Direct or 24 h culture

· Solid tumour:

· Within one week whenever possible

· longer risks overgrowth by normal fibroblasts

· failure rate:

· BM and blood:

· Not to exceed 10%

· Includes both culture failure and inadequate specimens

· Reporting:

· Comment on any change from previous studies

· Possible diagnoses

· Prognosis

· Other clinical correlations

References:

· CCMG Cytogenetic Practice Guidelines for Prenatal Samples, Feb 2010.

· CCMG Cytogenetic Practice Guidelines, 2003.