[Microtitration of anti-RH1 antibodies: interest in the follow-up of pregnant women].

UNLABELLED: The proposal for a 300 microg anti-RH1 injection at 28 GW by RH:-1 pregnant women complicates the interpretation of the screening for alloantibodies during pregnancy; to distinguish an alloantibody from a passive one is nevertheless important for the care of the patients. Testing a technique allowing this distinction seems thus necessary.

MATERIAL AND METHODS: The technique of microtitration of anti- RH1 antibodies is an indirect antiglobulin test. Two hundred specimens were tested in comparison with a standard prepared from a national anti- RH1 standard. If the anti- RH1 concentration measured is lower or equal to the expected concentration, there is a passive antibody. If the concentration is largely higher, we can suspect an allo-immunization.

RESULTS: With this technique, 38 alloanti- RH1 and 112 passive anti- RH1 antibodies were confirmed. Twenty-five diagnosis were modified: seven alloanti- RH1 initially labeled passive and 18 passive anti- RH1 previously considered as alloantibodies. 15 cases can not be concluded, because the blood sample was taking away too early after the injection, and 10 cases are on standby, waiting for a control.

DISCUSSION: The microtitration is an important exam in the follow-up of the RH:-1 pregnant women when an anti-RH1 antibody is found. This exam should be offered each time we have no information about the anti-D injection, or when an incoherent reaction compared to the presumed date of injection is observed.