What tests would be considered when investigating a delayed haemolytic transfusion reaction?

Delayed Hemolytic Transfusion Reaction (Immune Extravascular Reaction)

An immediate hemolytic transfusion reaction often is a dramatic event because the concentration of the antibody is high enough to cause immediate and appreciable RBC destruction. In many cases of hemolytic transfusion reaction, the transfused donor cells may survive initially, but after a variable delay (2-21 days), they are hemolyzed.248 This type of reaction occurs mainly in recipients sensitized to RBC antigens by previous blood transfusions or pregnancy. As a result, this delayed reaction is more common in females with a known disposition for alloimmunization. These delayed hemolytic transfusion reactions occur when the level of antibody at the time of transfusion is too low to be detected. RBC destruction occurs only when the level of antibody is increased after a secondary stimulus (i.e., anamnestic response). These delayed reactions are often manifested only by a decrease in the posttransfusion Hct. Jaundice and hemoglobinuria can occur in these patients and can cause some impairment in renal function, but only rarely do they lead to death. Unlike immediate reactions, antibodies most commonly involved in delayed hemolytic reactions are those in the Rh and Kidd systems rather than the ABO system. Although improved blood-banking procedures have decreased the incidence of immediate hemolytic transfusion reactions, the delayed hemolytic reaction may not be preventable, because pretransfusion testing is unable to detect very low levels of antibody present in potential blood recipients.

The surgical team should include in their differential diagnosis a delayed hemolytic transfusion reaction in any patient who has an unexplained decrease in Hb 2 to 21 daysafter a transfusion, even without obvious manifestation of hemolysis. This is especially important in a postoperative patient when the decrease in Hb may be attributed to postoperative bleeding and lead to a return to the operative room for additional surgery.

Abstract

Delayed hemolytic transfusion reactions (DHTRs) occur 3–10 days after the transfusion of RBC products that appear to be serologically compatible. These reactions occur in patients who have been alloimmunized to minor RBC antigens during previous transfusions and/or pregnancies; pretransfusion testing fails to detect these alloantibodies due to their low titer. After reexposure to antigen-positive RBCs, an anamnestic response occurs, with a rapid rise in antibody titer. Decreased survival of the transfused RBCs may result, primarily due to extravascular hemolysis. In the majority of cases, however, anamnestic antibody production does not cause detectable hemolysis. The term delayed serologic transfusion reaction (DSTR) defines reactions in which an anamnestic antibody is identified serologically, in the absence of clinical evidence of accelerated RBC destruction. Antigens implicated most often in DHTRs and DSTRs are in the Kidd, Duffy, Kell, and MNS systems, in order of decreasing frequency.

Delayed Hemolytic and Serologic Transfusion Reaction

Delayed hemolytic transfusion reactions (DHTRs), with an incidence of approximately 1:20,000 transfusions, occur when RBC transfusion precipitates an alloantibody response, resulting in decreased RBC survival. If an alloantibody response is noted in the absence of RBC destruction, it is termed a delayedserologic transfusion reaction (DSTR), which has an incidence of approximately 1:6000 transfusions. If alloantibodies are formed within days of transfusion, it is presumed to be an anamnestic alloantibody response in an individual who had previously formed antibodies, usually from an earlier transfusion or pregnancy. If alloantibodies are formed within weeks of transfusion, it is presumed to be a primary alloantibody response.

DHTRs are characterized by an unexpected decrease or less than expected increase in the recipient’s hemoglobin post-transfusion. Other signs and symptoms typically much less severe than those associated with acute hemolytic transfusion reactions include fever, chills, jaundice, malaise, back pain, and rarely renal failure. To prevent future reactions, the patient should receive antigen-negative RBCs for future transfusions. The primary mitigation strategy is prophylactic RBC antigen matching.

A severe form of DHTR is hyperhemolytic transfusion reaction. This rare reaction is most often reported in sickle cell and thalassemia patients and results in destruction of both donor and recipient RBCs, leading to more severe anemia. Additionally, the patients usually have reticulocytopenia. RBC allo- or autoantibodies may or may not be present. The pathophysiology remains unclear, but proposed mechanisms include innocent bystander hemolysis, suppression of erythropoiesis, and macrophage-mediated destruction. Treatment includes erythropoietin, intravenous immunoglobulin, steroids, rituximab, and eculizumab. Future RBC transfusions should be administered cautiously.

DELAYED HEMOLYTIC TRANSFUSION REACTION

Delayed hemolytic transfusion reactions (DHTRs) present with red blood cell hemolysis from 2 days to several months after a transfusion. Symptoms and signs include fever, mild jaundice, and an inexplicable decline in hemoglobin concentration. Other serious symptoms, more typical of an AHTR (e.g., renal failure, hemoglobinuria), are uncommon.

DHTRs commonly result in postoperative jaundice and may significantly lower the patient's hemoglobin level. The cause of DHTRs is the delayed generation of an antibody to a donor antigen to which the recipient has been previously exposed. The culprit antibody binds a non-ABO group such as the Rh, Kidd, Kell, or Duffy groups. The diagnosis of a DHTR may be difficult. A direct antiglobulin test is not positive until several days after the transfusion and then remains positive only while there are active symptoms.

Delayed Hemolytic Transfusion Reactions

Even when major and minor crossmatches indicate compatibility, delayed hemolytic transfusion reactions can occur days to weeks after transfusion. This is due to antibody production by either the donor or recipient B cells in response to exposure to antigens on red cells. Usually seen in patients who have had multiple transfusions or in multigravida women, these reactions may be unavoidable without complete RBC antigen typing, a procedure occasionally indicated for recipients of repeated transfusions. An incompatibility in the minor crossmatch does not usually result in a serious reaction, although the recipient's red cells can be hemolyzed if the titer of the antibody is sufficiently large. Fortunately, 90% of transfusions are now given as PRBCs, which contain a very small volume of plasma, thus minimizing the chance of a transfusion reaction occurring as a result of donor sensitization.

The signs and symptoms of a delayed hemolytic reaction include low-grade fever, a decrease in hemoglobin, mild jaundice, a positive direct antiglobulin test, and elevation of lactate dehydrogenase.

Treatment of a delayed hemolytic reaction is not needed unless there is evidence of brisk hemolysis. In the case of brisk hemolysis, treatment consists of fluids, antigen-negative (type O) blood transfusions, or red cell exchange.

Delayed hemolytic transfusion reaction

Delayed hemolytic transfusion reactions (DHTR) are caused by an anamnestic antibody response in the recipient precipitated by re-exposure to a non-ABO red cell antigen previously introduced by transfusion, transplantation or pregnancy. The antibody, often of the Kidd or Rh system, may be undetectable on pretransfusion testing but often increases rapidly in titer following the transfusion. DHTR due to a variety of red cell antigens have been extensively reported, and may be as high as 3.7% in patients undergoing HSCT.37 In one center's experience, red cell alloantibody formation to non-ABO antigens was more frequently seen in ABO-mismatched transplants; the preparative regimen/GvHD prophylaxis did not influence the development of these alloantibodies.37 Hemolytic reactions associated with infusion of donor immune cells are discussed under blood group incompatibility.38–40

Antibody cards

Delayed haemolytic transfusion reactions can occur when antibodies have not been detected in the current antibody screen or have been incorrectly identified.1 It has been suggested that antibody cards, produced either by the hospital or the reference centre, be carried by the patient for presentation on admission to hospital. To be effective, such cards have to be accompanied by patient information leaflets, explaining the significance of the antibodies and preferably handed personally to the patient by someone with a clear understanding of blood transfusion practice. There are potential pitfalls with this suggestion, not least that the level of proficiency in identifying antibodies and appreciating their clinical significance varies between establishments. A better long-term approach may be to have a national database of patients who have been identified as having clinically significant antibodies.

Delayed Hemolytic Reactions

Delayed hemolytic transfusion reactions can be seen several days to months after the transfusion. A decrease in hemoglobin level helps the clinician to make the diagnosis. The patient may report vague symptoms such as chills, myalgia, and low back pain. This reaction occurs as a result of the transfused RBCs becoming coated with antibodies and being removed by the tissue‐bound macrophages in the spleen. Patients may have previously been sensitized to minor blood group antigens, but their antibody levels fall below detectable levels during the cross‐match process. After transfusion, an anamnestic antibody response occurs, usually within 2 weeks. Only the transfused RBCs are destroyed, but occasionally this is enough to cause renal failure. If a delayed hemolytic reaction is suspected, blood should be sent to the blood bank for testing. Often the antibodies to these minor antigens will subside again, putting the patient at risk for recurrent problems. Treatment is supportive.

Definition and Incidence

Mollison24 defined DHTR as accelerated destruction of transfused red cells that begins only when sufficient antibody has been produced as a result of an immune response induced by the transfusion. Since the first case of DHTR attributed to Boorman and colleagues31 was reported in 1946, numerous cases have been described in the literature.32–37 Although exceptions are found,38–42 most DHTRs share these characteristics:

DHTRs generally occur in patients who have been alloimmunized to RBC antigens by previous transfusions or pregnancies.

Because the titer has decreased below detectable levels, the implicated antibody is not detected in pretransfusion antibody screening or compatibility testing.

DHTR is usually suspected 3 to 10 days after transfusion, when clinical symptoms associated with hemolysis are observed and/or serologic findings consistent with DHTR are noted (Table 49-4).

The clinical symptoms most frequently associated with DHTR include unexplained decreases in hemoglobin and hematocrit, fever, and jaundice.

The hallmark serologic findings in DHTR are the development of a positive direct antiglobulin test (DAT) and/or a positive antibody screening test in posttransfusion testing because of the presence of RBC antibodies that were not detected in pretransfusion testing.

Antibodies directed against Rh (CEce) and Kidd (Jka, Jkb) system antigens are the antibodies most commonly implicated in DHTR; however, numerous other specificities have been described.

The frequencies of DHTR reported in early studies vary widely.29,36 In the first series conducted at the Mayo Clinic from 1964 to 1973, the incidence of DHTR was reported as 1 DHTR per 11,650 RBC units transfused, with 22 (96%) of the 23 cases having clinical manifestations of hemolysis, and 3 deaths attributed to DHTR.29 In the second series from 1974 to 1977, the incidence of DHTR had increased to 1 DHTR per 4000 RBC units transfused, and only 24 (65%) of 37 had clinical evidence of hemolysis; the remaining 13 (35%) demonstrated serologic findings consistent with a DHTR, but no clinical or laboratory evidence of hemolysis was associated with transfusion.36 This trend of increased frequency, but decreased clinical significance, appears to be related, in part, to the manner in which DHTRs were defined. If the frequency of DHTR is determined on the basis of clinical reporting alone, then the incidence would be far lower than the true rate, because the signs and symptoms of hemolysis are nonspecific and may be difficult to distinguish from the complicated medical course of multitransfused patients.26,27 If DHTR is defined by posttransfusion serologic testing, then the frequency is likely to increase, and the clinical findings may diminish, because correlation between serologic results and clinical hemolysis is often poor.30

The definition of DHTR was clarified by Ness and colleagues30 in 1990, when the authors introduced the term delayed serologic transfusion reaction (DSTR) to describe cases with serologic evidence of DHTR (i.e., the development of a positive posttransfusion DAT result and a newly identified alloantibody in eluate studies or plasma studies or both), but no clinical evidence of hemolysis. The authors strictly defined DHTR as a subset of DSTR in which clinical evidence of hemolysis was attributable to a transfusion reaction. In their series at the Johns Hopkins Hospital, only 6 (18%) of 34 consecutive patients identified with serologic findings consistent with DHTR had clinical evidence of hemolysis associated with transfusion and could be defined as DHTR by strict definition. Twenty-eight (82%) of the 34 DSTR cases had no clinical evidence of hemolysis, as determined by retrospective chart review. The ratio of DHTR to DSTR can be expressed as 18:82 (Table 49-5). The combined frequency of DSTR and DHTR was calculated as 1:1605 (0.06%) RBC units transfused. The frequency of true DHTR was only 1 case per 9094 units (0.01%) transfused.

By using the same definitions as prescribed by Ness and colleagues,30 the Mayo Clinic reported a combined frequency of DHTR/DSTR as 1 per 1899 allogeneic RBC units transfused with a DHTR/DSTR ratio of 36:64 when patients were evaluated for clinical hemolysis concurrent with the detection of positive posttransfusion serology.43 The most recent study from the Mayo Clinic spanning the years 1993 to 1998 indicates a decline in DHTR and a concomitant increase in DSTR, which the authors attributed to the implementation of a more-sensitive antibody screening method and a decrease in the average length of hospital stay for inpatients.44 Interestingly, their current rates of observed reactions and the DHTR/DSTR ratio are very similar to those reported by Ness and colleagues30 in 1990 (see Table 49-5).

Delayed Hemolytic Transfusion Reactions and Delayed Serologic Transfusion Reactions

Together, delayed hemolytic transfusion reactions (DHTRs) and delayed serologic transfusion reactions (DSTRs) occur in approximately 1:2500 transfusions. DHTRs are hemolytic reactions that occur 24 h posttransfusion resulting from posttransfusion red blood cells (RBCs) alloantibody formation. DSTRs are also due to alloantibody formation, but there is no laboratory evidence of hemolysis.

Previously, the recipient mounted an immune response to foreign RBC antigens, most commonly through blood transfusions or via pregnancy (Speiss, 2004). The blood group antigens most often involved, in decreasing frequency, are Kidd, Duffy, Kell, and MNS (Mollison et al., 1997). Upon reexposure to the foreign antigen (e.g., via a second blood transfusion with antigen positive RBCs), the immune system increases its production of the antibody, leading to extravascular hemolysis in DHTRs. Extravascular hemolysis does not involve the release of RBC constituents directly into the circulation, but rather occurs within the confines of the reticuloendothelial system and rarely involves complement. If no detectable hemolysis is identified, the process is termed a DSTR. This process often takes anywhere from 2 to 14 days and can be very subtle in clinical presentation (Petrides, 2007).

Often, DHTRs are clinically suspected due to the lack of an appropriate response to RBC transfusion. In general, after transfusion, an adult patient's hemoglobin and hematocrit should rise to 1 g dl and 3%, respectively. When this does not occur and no other cause, such as occult bleeding, is identified, a possible delayed hemolytic transfusion reaction (DHTR) should be investigated. Other signs of DHTR include jaundice, anemia, fever, hemoglobinuria, and renal failure. In cases of DHTR, the antibody screen and crossmatch tests may be initially negative and become positive posttransfusion.

DHTRs are identified in the laboratory by a positive antibody screen and DAT; other labs may reveal an elevated lactate dehydrogenase (LDH), elevated bilirubin, and decreased haptoglobin. Once the responsible alloantibody is identified, the patient should receive antigen negative RBCs (for the corresponding antibody) to prevent future reactions. The patient may need to be aggressively hydrated to preserve kidney function, as free hemoglobin and RBC stroma is toxic to renal tubules (Josephson, 2013).