Laboratory findings:
(1) The mother is antigen-negative.
(2) The fetus is antigen-positive.
(3) The father of the fetus is atnigen-positive.
(4) The mother has antibody to the antigen in her plasma.
(5) The titer of the antibody rises during a pregnancy if the mother has been previously sensitized to the antigen.
(6) The direct antiglobulin test on the newborn's red blood cells will be positive. The presence of large amounts of antbody coating the fetal red blood cells may interfere with antigen typing..
(7) An eluate prepared from fetal red blood cells will show antibody to the antigen.
(8) The autocontrol for antibody testing in the mother will be negative.
Some of the antigens associated with HDN include:
(1) S or s
(2) U
(3) Kell: K or k, Kp(a) or Kp(b), Js(a) or Js(b)
(4) Diego: Di(a) or Di(b)
(5) Colton Co(a)
Differential diagnosis of a positive DAT (direct antiglobulin test) in cord blood:
(1) ABO-incompatibility between mother and fetus
(2) anti-D from Rhogam administration
(3) anti-D from maternal alloimmunization
(4) autoantibody (which is associated with a positive autocontrol)
