1 INTRODUCTION

Transfusion therapy with red blood cells (RBCs) is critical for patients with severe anemia and patients in need. However, this procedure comes with some risks, such as transfusion reactions, iron overload, RBC antigen alloimmunization, and transfusion-transmitted disease.1, 2 Therefore, many strategies have been studied and employed to decrease the risks of these complications, including judicious transfusion and mitigation strategies to prevent these side effects.3, 4

Development of RBC alloantibodies after transfusions is one of the complications after transfusion, which might cause severe transfusion reactions and acute/delayed hemolysis reactions.5, 6 Many factors have been studied and are known to be associated with RBC alloimmunizations.7 Multiple transfusions have been shown to be associated with alloantibody formation in patients who require frequent transfusions.8-11 Other reports have also revealed associations between disease and racial differences in recipients and donors with the incidence of alloantibody formation after transfusions.12, 13

The alloimmunization of RBC could not only result in cross-matching problems in pre-transfusion survey, but could also cause severe hemolytic and transfusion problems in the future.13 Therefore, identification of alloantibodies and a reduction in the rate of alloimmunization to decrease the formation of alloantibodies are the keys to prevent these complications.14 The aim of current study is to identify the antigen and alloantibodies in our patients and to study the relationship of alloimmunization with previous transfusion status.

2 MATERIALS AND METHODS

The transfusion records of transfusion recipients in the blood bank of Kaohsiung Medical University Hospital treated between 2015 and 2017 were enrolled in the study. Transfusion history, alloimmunization results, and antibody identification findings were retrospectively analyzed. The study was approved by the IRB for data acquisition at Kaohsiung Medical University Hospital (KMUHIRB-E(I)-20170023).

In the first part, we analyzed the alloantibodies found in the pre-transfusion survey. In brief, antibody screening tests were performed with a combination of three sets of group O RBCs provided by the National Blood Bank for clinically significant antigens. Sera with positive antibody screening tests were used for antibody identification. Antibody identification was performed using commercially prepared cell panels (Makropanel 16-K1385, Sanquin, Amsterdam, the Netherlands) with anti- (Rh, Kell, Duffy, Kidd, Lewis, MNS, P, Mia, and Dia) by manual polybrene test. Cold antibodies survived with MNS, P, Mia, and Dia antibodies. Antigen screening was also performed using standard antibody serum.

For the second part, patients with alloantibodies from the pre-transfusion survey were assessed for their previous transfusion history and medical history. Patients with newly found alloantibodies with no alloantibodies noted in previous transfusion surveys were recorded and calculated for the association of transfusion dose and timing from the first transfusion therapy in our hospital to the first time alloantibodies that were found. Statistical analysis was performed using SPSS 20.0.

3 RESULTS

In total, 56,422 transfusion records from Kaohsiung Medical University Hospital between 2015 and 2017 were enrolled. Among them, 1858 alloantibody episodes were found in the pre-transfusion survey. Anti-Mia, anti-E, and cold antibodies were the most common alloantibodies, with a total prevalence of 3.29% (1858/56,422) (Table 1 and Figure 1).

TABLE 1. Alloantibodies rate from 2015 to 2017 Year 2015 2016 2017 Alloimmunization no. /transfusion no. 526/18,922 666/18,349 666/19,151 Alloantibody rate % 2.78% 3.61% 3.48%

2015–2017 alloantibody identification analysis

Among 1858 alloantibody episodes, 130 episodes had a transfusion history in our hospital, with no alloantibodies identified in the previous pre-transfusion survey, while 1728 episodes were patients with a transfusion history with alloantibodies previously found in the pre-transfusion survey (Table 2). Tracing back to these 130 newly transfusion-induced alloantibodies, antibodies were found with a mean of 10.8 ± 7.8 units of packed RBC (pRBC) transfusion, a mean of 66.3 ± 52.8 days (Table 2), and with a mean of 4.3 ± 2.7 times of transfusion from the first transfusion. Anti-E was the most frequent newly identified alloantibody after transfusion, with a mean of 17.4 ± 8.9 units of pRBC transfusion, a mean of 21.5 ± 19.1 days, and a mean of 7.5 ± 5.4 times of transfusion from the first transfusion therapy.

TABLE 2. Mean dose and days of 130 episodes with newly found alloantibodies after first transfusion AlloAb No. (rate) Mean doses of pRBCa transfusion (units ± SD) Mean days from first transfusion (days ± SD) Total 130 10.8 ± 7.8 66.3 ± 52.8 E 48 (36.9%) 17.4 ± 8.9 21.5 ± 19.1 Mia 41 (31.5%) 10.8 ± 8.9 68.7 ± 65.3 Cold AutoAb 27 (20.7%) 13.5 ± 7.1 35.1 ± 7.4 C + e 4 (3.1%) 10.0 ± 8.7 23.0 ± 5.7 Dia 4 (3.1%) 22.5 ± 13.7 50.2 ± 19.0 Fyb 1 (0.8%) 8 81 M 2 (1.5%) 6 6 Jka 1 (0.8%) 10 72 P1 1 (0.8%) 15 59 S 1 (0.8%) 6 59

Therefore, we checked the Rh-E antigen of the RBC in 9182 patients during the pre-transfusion screening (Table 3). The results revealed that Rh-ee (62.1%) was the most common phenotype in our population, followed by Rh-Ee and Rh-EE (31.8% and 5.9%, respectively).

TABLE 3. The distribution of antigens of RHE and RHe RH phenotype Rh-Ee Rh-ee Rh-EE Rh-Ee0a Counts (no.) 2926 5689 546 21 Percentage 31.8% 62.1% 5.9% 0.20% a Ee0 means none existence of RHE antigen and Rhe antigen or unidentified. 4 DISCUSSION

An analysis of the literature found that alloantibodies were found at rates ranging from 0.3% to 38% of the population, depending on the different study groups and study methods.15, 16 In general, RBC alloantibodies were detected in approximately 1%–2% of the hospital-based population and increased to 2%–9% of patients after transfusion of one or more units of RBCs.17, 18 In our study, the alloantibody rate was 3.29% from a hospital-based survey, which was similar to other studies. Anti-Mia, anti-E, and cold antibodies were the most frequent alloantibodies in our population, which is similar in the Eastern area.13, 19-22 However, anti-K, one of the common alloantibodies in other areas, is not common in our population.7, 12, 23

There are many factors affecting patients with RBC alloantibodies, one of which is previous transfusion exposure.24, 25 From our survey, alloantibodies developed after previous transfusion with a mean of RBC of 10.8 ± 7.8 units, a mean of days of 66.3 ± 52.8, and a mean of 4.3 ± 2.7 times of transfusion from the first transfusion. Therefore, how to keep these patients from RBC alloimmunization might be an issue, given that the patients subsequently required frequent transfusion.24 Currently, judicious transfusion of RBCs is the primary strategy to prevent RBC alloimmunization. Mitigation strategies with matched RBC antigens of blood donors to recipients or providing immunomodulatory agents are also employed in clinical practice with some benefit.3, 8, 24 In our study, Rh-ee was the most common phenotype, which is vulnerable to the development of anti-E antibody.26 Fortunately, the Rh-ee phenotype is the most common phenotype in our population, which could also provide sufficient blood donation for transfusion needs. Therefore, with the fact that anti-E is the most common alloantibody in our population and Rh-ee is the most common phenotype, a strategy involving the provision of Rh-ee blood for Rh-ee recipients to prevent alloimmunization with anti-E would be reasonable for our population. Although reasonable, further studies on the cost–benefit are warranted for the use of Rh-ee blood for Rh-ee patients, considering the burden of health reimbursement. With the efforts of the Taiwan Blood Services Foundation, antigen identification on blood products has been promoted and labeled for clinical use. This supports our proposal to provide Rh-ee blood to Rh-ee recipients. However, more studies on the cost-effect benefit of this protocol are warranted for a clear conclusion.

In this real-world study, there are some limitations of the study, including the lack of antigen data of previous transfused RBC products, which would hamper the estimated duration from transfusion to the occurrence of alloantigens. More than half of the patients (83/130) had hematologic disease, and some of them (39/130) had infection episodes during the survey period, which would impact the production of alloantigens.

In summary, we studied the hospital-based transfusion screen and found that the RBC alloantibody rates were present at rates of 3.29%, with anti-Mia, anti-E, and cold antibodies being the most frequent alloantibodies. Anti-E was the most common newly developed alloantibody after transfusions, and Rh-ee was the most common phenotype in our population. Therefore, the use of Rh-ee blood for Rh-ee recipients could be a good strategy for patient safety in our population.

CONFLICT OF INTEREST

All authors declare no conflict of interest.

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