Evaluation of the enzyme test for the detection of clinically significant red blood cell antibodies during pregnancy.

In the Croatian transfusion medicine, no general agreement has yet been achieved whether red blood cell (RBC) Rhesus (Rh) antibodies detected during pregnancy only by enzyme tests can cause hemolytic disease of the newborn (HDN). Results of the detection of clinically significant RBC antibodies by low-ionic-strength additive solution antiglobulin test (LISS-IAT) and trypsin enzyme test in 22,947 pregnant women are presented. All pregnant women in whom clinically significant RBC antibodies (RBC-CSA) were detected by LISS-IAT and/or enzyme tests were followed and observed during pregnancy. The women who had enzyme-only anti-D antibodies in their serum were followed up during subsequent pregnancies. Out of 302 positive results obtained by both techniques, irregular clinically significant enzyme-only antibodies (anti-RhD and anti-RhE specificity) were detected in 14 (4.6%) pregnant women. None of 11 RhD positive newborns whose mothers had enzyme-only anti-D antibodies, had signs of HDN after delivery. In these 11 women, anti-D antibodies were detected by LISS-IAT in the first trimenon of subsequent pregnancy. Nine infants born from subsequent pregnancies to women who had previously had enzyme-only anti-D, had clinical signs of HDN. The authors concluded that there is no need for enzyme tests in prenatal testing because enzyme tests are not reliable in the prediction of HDN.

[The effect of Rh-D immunoprophylaxis with hyperimmune anti-D-immunoglobulin on the occurrence of RhD immunization in pregnancy]. / Utjecaj provodenja RhD-imunoprofilakse hiperimunim anti-D-imunoglobulinom na ucestalost RhD-imunizacija trudnica.

During prenatal immunohaematological examination in the period from January 1, 1991 to December 31, 1995, in the Croatian Institute of Transfusion Medicine we tested sera of 5107 RhD negative women. All of them had pregnancies in their medical history. The frequency of Rh immunization was 4.6% in 1991; 4.1% in 1992; 2.5% in 1993; 2.5% in 1994 and 2.4% in 1995. Rh immunization during the first pregnancy was observed in 0.46% of women, in 1.8% during the second, in 9.4% during the third, in 22.4% during the fourth pregnancy, and 33.8% in women with more than five pregnancies. In women that have no abortions in their medical history, anti-D alloantibodies were found with the frequency of 0.46% at the end of the first pregnancy, 1.2% at the end of the second pregnancy, 5.9% at the end of the third pregnancy, 14.3% at the end of the fourth pregnancy, and 15.3% in women with more than five pregnancies. The frequency of anti-D alloantibodies in women who in their medical history have only abortions is 3.4% after the first abortion, 10.5% after the second, 17.8% after the third and 20.8% after the fourth or more abortions. The frequency of antibodies of anti-D specificities in women who had abortions and births is 17.1% at the end of the third pregnancy, 26.2% at the end of the fourth pregnancy, and 42.7% after more than five pregnancies. The frequency of anti-D alloantibodies in women who were protected from Rh immunization by hyperimmune anti-D globulin is 1%. The obtained results demonstrate that prevention of Rh immunization by hyperimmune anti-D globulin does not comprise all the Rh negative women, and is especially inadequate after abortions and multiple pregnancies.

[Evaluation of the direct antiglobulin test]. / Evaluacija direktnog antiglobulinskog testa.

The validity of a direct antiglobulin test (DAT) was evaluated by testing 7645 blood samples from hospitalized patients. DAT was routinely done in 7201 blood samples sent for pretransfusion testing and 444 blood samples specifically sent for the examination of immune hemolysis. Positive DAT was discovered in 0.04% (3/7201) pretransfusion samples and in 3.83% (17/444) samples examined for immune hemolysis. In 16 of the samples with positive DAT, IgG antibodies with or without complements and in 4 samples only components of complements were detected on RBC. The cost of positive DAT in pretransfusion testing is 92 times higher than that of DAT during laboratory investigation of immune hemolysis. Due to a low frequency of positive DAT during pretransfusion testing, its cast and the fact that patients had no clinical signs of immune hemolysis, we advocate no use of a routine DAT during pretransfusion testing.

Alloimmunizations following blood transfusions.

A retrospective study was performed to estimate the rate of alloimmunization against red blood cell (RBC) antigens in hospitalized patients and the frequency and specificity of clinically significant alloantibodies (CSA) detected during routine pretransfusion testing of 10,641 blood samples. Clinically significant alloantibodies were found in 116 out of the 10,641 tested serums (1.09%). The incidence of CSA in two surgical groups of patients was 0.18% and 0.68%, respectively. In patients with hematologic diseases the frequency of CSA was 17.6%, in patients with uremic disease it was 14%, and in patients with cirrhosis hepatis it was 6.9%. The incidence of clinically significant alloantibodies in patients who had one to five exposures to RBC antigens was 5.1%; in patients who had six to fifteen exposures, 87.9%; and in patients with more than fifteen exposures, 6.8%. The most frequently found single alloantibodies were anti-Kell (22%), and the following irregular alloantibodies were found with decreasing frequency: anti-E (20%), anti-D (11%), anti-c (10%), anti-C (7%), anti-Kidd (6%). The most frequent alloantibodies found together with other alloantibodies had anti-Duffy specificity (80%), and the following irregular alloantibodies were found with decreased frequency: anti-C (70%), anti-c (57%), and anti-Kidd (50%).