The Rosette test is commonly used to detect small numbers of fetal RhD-positive red cells in the circulation of a RhD-negative mother in postnatal analysis to establish whether she may require anti-D immunoglobulin. WCBS has stopped performing this test as it is not in our scope of practice. Please note that both the Rosette (qualitative) and Kleihauer-Betke (quantitative) tests are available from pathology testing laboratories.

In postnatal testing, WCBS performs the sodium hydroxide test on the cord and maternal samples for rapid verification of foetal blood (cord sample) from adult blood (maternal sample).

The cord sample undergoes:

  • Rh-typing to determine if the infant is RhD-negative, RhD-positive or RhDweak positive. If the mother is RhD-negative and the infant is either RhD-positive or RhDweak positive, treatment of the mother with anti-D immunoglobulin may be necessary to prevent Haemolytic Disease of the Foetus and Newborn (HDFN) in future pregnancies.
  • A direct antiglobulin test (DAT) to specifically detect in vivo red cell sensitisation to the D antigen that may indicate a potential case of HDNB in the infant.
  • ABO blood grouping (forward grouping only).

The maternal sample undergoes:

  • Rh-typing.
  • An indirect antiglobulin test (IAT) to detect the presence of abnormal IgG antibodies that could cause HDNB in future pregnancies. The likelihood of HDNB in future pregnancies is high especially if the infant has a positive DAT.  Where the IAT and DAT are positive, the antibody needs to be identified, so as to select corresponding antigen negative blood in the event of an exchange transfusion. The type of antibody will be reported to the requesting clinician, for future record purposes.
  • ABO blood grouping (forward and reverse grouping).
  • Anti-D titration, if necessary.

For more information about postnatal testing, please contact your nearest Blood Bank.