Postnatal Diagnosis (Blood Culture)

Chromosome studies are requested where problems that may have a cytogenetic basis are suspected – such as in cases of babies with birth defects, issues with puberty,  or adults with fertility problems. Additionally, prospective gamete donors are screened to detect carriers of balanced chromosome rearrangements.

Please note: For children with developmental delay and physical handicaps, high-resolution CGH is now the recommended frontline test (4–5ml blood in EDTA would be required).

Samples

Lithium heparin whole blood specimens are required – gently mixed to prevent clotting and must not be frozen, See sample stability section for cytogenetic samples. Sample volumes may be reduced for children (2–4ml) and neonates (1–2ml).

Turnaround time

The usual turnaround time is 2-3 weeks however the laboratory will endeavour to respond to urgent requests. Where a major trisomy is suspected, a rapid PCR screen may be performed to provide an urgent provisional result.

Notes

• Rarely, blood samples fail to culture (in less than 1% of cases);
• The culture may yield chromosomes of insufficient quality. This will be indicated on the report and a repeat study suggested;
• The laboratory should be informed of the patient's natal/biological sex, particularly if this differs from the identified gender.
• The laboratory should be informed if the patient has recently received a blood transfusion.
• The laboratory should be informed if the patient has EVER had a bone marrow transplant.