Constitutional analysis is performed on venous blood samples (lithium-heparin 5ml). Chromosomes are prepared from cultured blood lymphocytes.
Molecular cytogenetics (FISH) can also be performed on these samples.
The main referral categories are: mental retardation or developmental delay; infertility and recurrent pregnancy loss; dysmorphism and congenital abnormality. Referrals are via general practitioners, or specialist clinics. Reports are available within 28 days for routine samples, or within 10 days for urgent referrals. Urgent samples would include neonates, parents of an ongoing pregnancy or specific clinical requests.
Chromosome studies may provide a diagnosis in cases of mental retardation or congenital abnormality, or may reveal familial rearrangements responsible for recurrent pregnancy loss. Liaison with the clinical genetics team allows patients to benefit from counselling, with respect to prognosis for the affected individual, and risks of recurrence for other family members