Down syndrome is confirmed through cytogenetic studies which confirm trisomy 21. In addition complete blood count with differentials is performed to rule out leukemia, TSH and T4 are performed at birth, 6 months, 1 year and then annually to rule out hypothyroidism. Low level of IgG subclass 4 are correlated with bacterial infections. The mosaic trisomy 21 includes lymphocyte preparations, FISH, buccal mucosa cellular preparations and scoring frequency of trisomic cells.

• The following lab tests are done for the patients of Down syndrome to rule out conditions associated with down syndrome:^[1][2]
  • CBC with differentials to rule out Leukemia
  • To rule out hypothyroid, the following tests are performed at birth, 6 months, 1 year and then annually:
    • TSH
    • T4
  • Cytogenetic studies
    • Cytogenetic studies are performed for the confirmation of down syndrome
    • Karyotyping must be performed to determine the risk of recurrence
  • Measurement of Immunoglobulin G
    • Subsequent low level of IgG subclass 4 are correlated with bacterial infections
  • The Mosaic trisomy 21 that includes:
    • Lymphocyte preparations
    • FISH
    • Buccal mucosa cellular preparations
    • Scoring frequency of trisomic cells
  • Interphase fluorescence in situ hybridization (FISH)
    • Interphase fluorescence in situ hybridization is used for early and rapid detection of trisomy 21
    • The FISH test is beneficial in the diagnosis of Down syndrome in prenatal and neonatal period
    • The FISH test needs to be confirmed by a complete karyotype analysis as it does not provide information about the trisomy 21 to weather if it is secondary to a translocation