Increased red cell destruction in the absence of demonstrable antibodies in vitro

Immune hemolytic anemia associated with negative routine serology

Immune hemolytic anemia can occur in patients who have no antibodies detectable by routine procedures (direct [DAT] and indirect [IAT] antiglobulin tests). DAT-negative autoimmune hemolytic anemias (AIHAs) represent 5% to 10% of all AIHAs. Three causes have been identified: (1) small numbers of red blood cell (RBC)-bound IgG molecules below the threshold of the DAT; (2) IgA and IgM autoantibodies; and (3) low-affinity autoantibodies. Antibody-independent cytotoxic events caused by natural killer (NK) cells have also been implicated. DATs are sometimes found to be positive when tested by reference laboratories, due to poor technique in reading antiglobulin tests in hospital laboratories. Hemolytic transfusion reactions also can occur when no alloantibodies are detectable by routine procedures. In some cases antibodies can be detected by special serologic procedures (such as the Polybrene test); in other instances phenotypically matched RBCs survive well and a specific antigen can be shown to be involved, suggesting a specificity (like anti-C) that is undetectable by any technique. Antibodies other than to blood group antigens, such as human leukocyte antigen (HLA) antibodies, may sometimes be involved.

Nondeletional ABO*O alleles frequently cause blood donor typing problems

BACKGROUND

Difficulties in the demonstration of expected isoagglutinins is a common problem in ABO reverse typing. Some nondeletional ABO*O alleles have been shown to encode for the expression of minimal amounts of A antigen, resulting in very weak anti-A activity in some cases. It is unknown whether minor problems with ABO reverse typing are related to specific ABO*O alleles.

STUDY DESIGN AND METHODS

Among 2196 blood group O red cell (RBC) donations, the ABO alleles of those donations in which the isoagglutinins were incorrectly identified were analyzed with an autoanalyzer. The presence of nondeletional ABO alleles was determined by sequence-specific priming and sequencing.

RESULTS

Fifty (2.3%) of the group O RBC donations tested had to be typed manually because of isoagglutinin detection problems in automated typing: reduced anti-A activity was observed in 45 cases, reduced anti-B activity in 4 cases, and variably reduced isoagglutinin activity in 1 case. The nondeletional ABO*O alleles ABO*O03 and ABO*Aw08 were implicated in 38 of these 50 cases (1.7% of all blood group O donors). The remaining samples, including those with reduced anti-B activities, were homozygous for deletional ABO*O alleles.

CONCLUSION

Nondeletional ABO*O alleles are the most frequent cause of isoagglutinin detection problems in blood group O donors.

[Immuno-hemolytic transfusion reactions. IV. Analysis, risks and prevention]

The immunological risk of red blood cell transfusions now seems higher than the viral risk. According to studies, severe accidents due to blood incompatibility occur with a frequency estimated at 1/6000 to 1/29000; despite technical progress, the risk does not significantly diminish. The majority of accidents do not originate from laboratory or production stages but from defects in the application of clinical procedures. Preventive measures are based on (i) the elaboration of clinical guidelines, (ii) the compliance to strict rules in carrying out bedside ABO check, and (iii) the realization and interpretation of antibody screening tests. The implementation of quality assurance systems and of the epidemiological surveillance system, which define the basis of a prevention policy, leads to the expectation of an improvement of transfusion safety.

Blood transfusion in the para-Bombay phenotype

The H-deficient phenotypes found in Chinese so far, have all been secretors of soluble blood group substances in saliva. The corresponding isoagglutinin activity (e.g. anti-B in OB(Hm) persons) has been found to be weak in all cases. To determine the clinical significance of these weak isoagglutinins 51Cr red cell survival tests were performed on three OB(Hm) individuals transfused with small volumes (4 ml) of groups B and O RBC. Rapid destruction of most of the RBC occurred whether or not the isoagglutinins of the OB(Hm) individuals were indirect antiglobulin test (IAGT) reactive. When a larger volume (54 ml packed RBC) of group B cells (weakly incompatible by IAGT) was transfused to another OB(Hm) individual with IAGT active anti-HI, the survival of the transfused RBC was 93% at 24 h, with 30% of the RBC remaining in the circulation at 28 d in contrast to 76% as would be expected if the survival was normal. Therefore when whole units of blood of normal ABO blood groups, compatible by IAGT, are transfused, the survival is expected to be almost normal. These weak isoagglutinins may not be very clinically significant and we suggest that when para-Bombay blood is not available, the compatibility testing for OA(Hm) persons should be performed with group A and group O packed RBC; OB(Hm) with group B and group O packed RBC: OAB(Hm) with groups A, B, AB and O packed RBC. For cross matching, the indirect antiglobulin test by a prewarmed technique should be used.

Intravascular hemolytic transfusion reaction without detectable antibodies: A case report and review of literature

A case of intravascular hemolytic transfusion reaction without detectable antibodies occurring in a 55-year-old male is reported. Specificity for the C antigen in the Rh system was demonstrated by technetium-99m red cell survival studies. A cell-mediated mechanism of hemolysis was suspected and investigated. Previously reported cases are reviewed and discussed. The entity of intravascular hemolytic transfusion reaction associated with minimal symptoms and no detectable antibodies deserves further investigation.

The phenotype Ae1B: a probable result of chimerism

An apparently normal healthy adult with the blood group phenotype Ae1B is described. The unusual ABO group is apparently the result of chimerism, the proportion of the minor population of cells being so small as to be only detectable by absorption and elution techniques.

Absent left hemidiaphragm, arhinencephaly, and cardiac malformations

An infant is reported with absent left hemidiaphragm, hydrocephalus, arhinencephaly, and cardiovascular anomalies. The parents are second cousins.