Use of the gel agglutination technique for determination of fetomaternal hemorrhage.
BACKGROUND
Adequate administration of Rh immune globulin requires an accurate determination of the number of D-positive cells in the circulation of D-negative women. Although several tests have been described for the detection of fetomaternal hemorrhage, there is still a need for a rapid, simple, and clinically relevant screening test.


METHODS
Serial dilutions of a monoclonal anti-D were incubated with stock solutions (0.2 mL) of adult D-negative red cells in the absence or presence of various amounts of fetal D-positive cells (0.1, 0.2, 0.3, 0.4, and 0.5%). After incubation, the supernatants were tested against D-positive red cells by using the new, gel agglutination technique (GAT). After the GAT was adapted to detect D-positive cells at concentrations of > or = 0.2 percent, unselected postpartum samples from D-negative women (n = 420) who delivered D-positive infants were analyzed by both the new test and the Kleihauer-Betke test (KBT).


RESULTS
Three of a total of 420 postpartum samples were positive (> or = 0.4% fetal cells), and 406 were negative in both tests. One had 0.5-percent fetal cells in the KBT and gave negative results in the GAT. The latter test was, however, performed after administration of Rh immune globulin. The KBT gave false-positive results in two cases, because of hereditary persistence of hemoglobin F, and the GAT gave a false-positive reaction in one case because of a maternal weak D variant. In the remaining seven cases, the KBT results were only weakly positive (0.2%) and could not be attributed solely to D positive red cells.


CONCLUSIONS
The GAT is suited for routine screening. It provides rapid and specific detection of D-positive red cells at clinically relevant concentrations. The test may (rarely) yield false-negative results due to insufficient administration of Rh immune globulin before testing.
Salama
A
A
Department of Internal Medicine, Virchow Hospital, Humboldt University, Berlin, Germany.
David
M
M
Wittmann
G
G
Stelzer
A
A
Dudenhausen
J W
JW
D000328:Adult; D000372:Agglutination Tests; D005260:Female; D005331:Fetomaternal Transfusion / Q000175:diagnosis*; D006801:Humans; D011247:Pregnancy