Cytogenetics (constitutional)

Last updated: Monday, 06, August, 2007

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Item Process
Specimen

Blood is collected aseptically into sterile heparinised containers. All specimens must be delivered immediately to the laboratory.

Infant: 1-2 mL of cord or peripheral blood
Child: 5 mL blood
Adult: 5-10 mL blood

Skin biopsies (for fibroblast culture) should be full thickness (2-3 mm in depth) obtained aseptically and placed into sterile saline or tissue culture medium.

Method

Cultures of blood cells or fibroblasts are used, depending on clinical requirements.

Whilst results of blood cell cultures may be available within 3 days, fibroblast cultures may take up to 3 weeks for completion.

Cytogenetic harvesting, slidemaking, banding and karyotyping are performed on all specimens.

Application

Investigation of congenital anomalies;
psychomotor delay;
growth retardation;
recognisable syndromes;
delayed puberty; infertility;
recurrent spontaneous abortion (test both parents); and
microdeletion syndromes,see also FISH (Fluorescence in situ hybridisation).

Studies should be performed on the affected individual and sometimes family members may also require investigation.

Molecular genetics has now replaced cytogenetics for the diagnosis of Fragile X syndrome.

Interpretation

Findings are reported in terms of numerical and/or structural chromosome abnormalities (eg, deletions, translocations) - consult pathologist.

Reference

Rooney DE ed. Human Cytogenetics, Constitutional Analysis, a Practical Approach. Oxford University Press 3rd ed 2001. 

Gardner RJM and Sutherland GR. Chromosome Abnormalities and Genetic Counselling. 3rd ed. Oxford University Press 2004.