Immunohematology Feed

To contributors to the 2025 issues

Wed, 31 Dec 2025 00:00:00 GMT

Evanescence and persistence of red blood cell antibodies over time: a single-center experience

Wed, 31 Dec 2025 00:00:00 GMT

Alloantibodies may develop after exposure to foreign red blood cell (RBC) antigens. Evanescence occurs when an antibody falls below the sensitivity threshold of methods used in pretransfusion testing. An alloantibody that has evanesced may go undetected, resulting in possible delayed hemolytic transfusion reactions, which lead to increased morbidity and mortality. A survey was conducted to analyze evanescence of alloantibodies over time. A total of 544 patients with 656 alloantibodies were evaluated. Median follow-up was 294 days (range 3–3852 days). Analysis showed that patient age at detection of alloantibody (p = 0.037), sex (p < 0.001), results of initial RBC antibody screen (p < 0.001), RBC transfusion (p < 0.001), length of follow-up period (p < 0.001), and alloantibody specificity (p = 0.004) significantly influenced the time of evanescence. Evanescence rate was the highest for anti-Jka, anti-C, and anti-M and the lowest for anti-Fya and anti-D specificities. Evanescence of alloantibodies represents a significant problem in routine pretransfusion testing. Beyond improving testing by implementing more sensitive methods, there is a place for preventive usage of extended antigen-matched RBC units or the application of post-transfusion protocols. Sharing of antibody information across centers can also improve transfusion safety in these centers.

The Indian (IN 023) blood group system: an update

Wed, 31 Dec 2025 00:00:00 GMT

This update of the Indian (IN 023) blood group system (Xu Q. The Indian blood group system. Immunohematology 2011; 27:89–93) focuses on the discovery and clinical significance of new antigens, antibodies, and genetics since that review. The system now comprises six antigens, of which the more recently identified antigens are high-prevalence antigens (HPAs) IN:005 (INRA) and IN:006 (INSL); rare individuals lacking these antigens are found among the people from the Indian subcontinent. The Indian (IN) antigens are located on CD44, a single-pass transmembrane glycoprotein encoded by the CD44 gene on chromosome 11 at position p13. The absence of these HPAs is associated with homozygous missense mutations in CD44: 255C>G in exon 3, c.449G>A in exon 5 (for IN:–5, p.Arg150His), and c.276C>A in exon 3 (for IN:–6, p.His92GIn).

Cephalosporin-induced hemolytic anemia: a case study

Wed, 31 Dec 2025 00:00:00 GMT

Drug-induced immune hemolytic anemia (DIIHA) represents a rare but dangerous medical condition that more often affects children who are administered cephalosporins. A 10-year-old girl developed severe hemolysis after administration of cefuroxime and ceftriaxone for treating an infection linked to parotid lymphangioma. The patient had previously tolerated ceftriaxone and clindamycin but developed dizziness, pallor, and tachycardia, and her hemoglobin (Hb) levels decreased from 12.9 to 2.6 g/dL during her fourth day of treatment, which led to hypovolemic shock and transient renal dysfunction. Our objective is to establish cefuroxime and ceftriaxone as the responsible drugs for DIIHA through immunohematologic testing. The laboratory tests included the direct antiglobulin test (DAT) and the indirect antiglobulin test (IAT) along with drug-dependent antibody testing using the patient’s serum (1) to react against group O red blood cells (RBCs) treated with cefuroxime and (2) to react separately against group O RBCs not treated with, but in the presence of, ceftriaxone, with and without complement, at both room temperature and by the IAT. The DAT showed positivity for IgG and C3d. The patient’s serum reacted with cefuroxime-treated RBCs by the IAT and reacted with untreated RBCs when ceftriaxone and complement were present. The laboratory results showed that drug-dependent antibodies were present to target RBCs. The patient’s condition improved rapidly after stopping cephalosporins and starting ciprofloxacin/levofloxacin and clindamycin, which resulted in an Hb increase to 9.1 g/dL within 48 hours and the absence of hemoglobinuria. This case shows why health care professionals must identify DIIHA early through diagnostic testing even when patients have shown previous tolerance to antibiotics. This case report also shows that both cefuroxime and ceftriaxone were the drugs responsible for the DIIHA.

Wed, 31 Dec 2025 00:00:00 GMT

Improving transfusion outcomes in sickle cell disease through extended red blood cell molecular matching

Wed, 31 Dec 2025 00:00:00 GMT

We evaluated the impact of extended red blood cell (RBC) molecular matching on alloimmunization and transf usion-related outcomes in patients with sickle cell disease (SCD) and assessed the frequency and clinical significance of genotype– phenotype discrepancies. We conducted a retrospective analysis of 108 transfused patients with SCD who underwent phenotyping and molecular genotyping for clinically relevant RBC antigens. Patients were divided into two groups: those who received extended serologically matched RBC units (n = 55) and those who received extended molecularly matched RBC units (n = 53). Primary outcomes included the rate of alloimmunization, incidence of delayed hemolytic transfusion reactions (DHTRs), and the identification of antigen mismatches or discrepancies between genotype and phenotype. Molecular testing revealed clinically significant antigen mismatches in 42 percent of patients. Partial RH alleles were identified in 17 percent of patients. Discrepancies between genotype and phenotype were observed in 21.3 percent of patients. Alloimmunized patients were significantly more likely to have undetected mismatches. DHTRs after transfusion with RBC units that were serologically matched, but not molecularly compatible, were observed in two patients. In conclusion, extended RBC molecular matching improves the detection of clinically relevant antigen mismatches not identified by routine serologic methods and is associated with a lower risk of alloimmunization and transfusion-related complications.

The second reported case of a hemolytic transfusion reaction caused by anti-Sc2: a clinical diagnosis

Wed, 31 Dec 2025 00:00:00 GMT

SC2 is a low-prevalence antigen of the Scianna blood group system, historically associated with hemolytic disease of the fetus and newborn and only one prior case of hemolytic transfusion reaction (HTR). We report a second case of anti-Sc2–mediated HTR in a 33-year-old woman with β-thalassemia major and a history of anti-Sc2. She presented for routine transfusion and received 1 group O, D–E–K–S–Jk(a–) red blood cell (RBC) unit that was crossmatch compatible by the antihuman globulin (AHG)–polyethylene glycol testing method. Shortly after the transfusion, she developed chills and back pain that resolved with meperidine. Several hours later, she experienced jaundice, dark urine, and fatigue. Laboratory evaluation revealed a hemoglobin drop below the pre-transfusion baseline, elevated bilirubin (8.0 mg/dL, reference range ≤1.2 mg/dL), and a 2+ incompatibility between the post-transfusion sample and the donor RBC unit segment. Although the direct antiglobulin test and the antibody screen remained negative, reference testing confirmed anti-Sc2 in the post-transfusion plasma, and the donor RBC unit was Sc2+. This case reinforces the clinical relevance of anti-Sc2, highlights limitations of conventional antibody screening and the AHG crossmatch in detecting low-prevalence antigens, and supports the need for heightened clinical suspicion and individualized transfusion strategies, including additional targeted pre-transf usion testing, early consultation with reference laboratories, and sourcing of antigen-negative units in patients with known rare alloantibodies.

Fri, 31 Oct 2025 00:00:00 GMT

Loss of D expression associated with hematologic disease progression: a case report and review of the literature

Fri, 31 Oct 2025 00:00:00 GMT

We report a case of a 61-year-old male patient with a complex hematologic history including pre-B acute lymphocytic leukemia, allogeneic stem cell transplant, and newly treated colon cancer followed by diagnosis of high-risk myelodysplastic syndrome (MDS), who exhibited abolishment of D antigen production. The patient’s red blood cells (RBCs), which originally typed as group A, D+, again typed as group A, D+, after receiving stem cells from a female donor with the same blood type. The reactivity of the patient’s RBCs was strong when tested with anti-D reagent until he was treated for colon cancer. Within 6 months of diagnosis of cancer, he developed a mixed-field D typing result followed by a complete D– phenotype over the course of a few weeks, coinciding with the new diagnosis of MDS and initiation of immunosuppressive therapy. Polymerase chain reaction (PCR) testing revealed no weak or partial D variants, and subsequent Sanger sequencing confirmed the presence of a conventional RHD gene. A more focused analysis by chromosomal microarray identified deletions involving the RHD locus, supporting the hypothesis that active MDS disrupted gene expression. The patient received another stem cell transplant, this time from a group AB, D+ male donor. In a short period of time, MDS re-emerged along with re-identification of microarray mutations encompassing RHD in female cells (from the first donor) even after the second stem cell transplant. However, D expression remained strong, underscoring the presence of enough male donor RHD expression to maintain the D+ phenotype.

Prevalence and characteristics of irregular antibodies in northern Vietnamese blood donors

Fri, 31 Oct 2025 00:00:00 GMT

Irregular antibodies with the potential for causing transfusion reactions can be detected in healthy donors. The prevalence and characteristics of irregular antibodies in many populations are well known; however, the data of Vietnamese blood donors have not yet been reported. Our study was performed to assess the frequency and specificities of irregular antibodies among healthy blood donors in the north of Vietnam. A total of 199,281 blood donor samples were screened for irregular antibodies from 2021 to 2023. Antibody screening was performed by both microplate and tube methods. Positive tests were further confirmed using a gel card method. Subsequently, antibody identification was performed. The occurrence of a positive antibody detection test was 0.37 percent. Most cases had only one antibody (99.1%); the proportion of donors who had two and three antibodies accounted for 0.8 and 0.1 percent, respectively. The most frequently identified antibodies were of the MNS blood group system, with anti-Mia being the highest (72.7%) and then anti-M (12.9%), followed by the Lewis blood group system with anti-Lea (6.5%) and anti-Leb (2.4%). The results show the rate and characteristics of irregular antibodies in northern Vietnamese blood donors. These findings provide essential data to support recommendations for implementing antibody detection in donor testing nationwide. Moreover, the results underscore the importance of selecting appropriate reagent panels.

Performance of 0.8 percent reagent red blood cell panels after extended on-board analyzer utilization

Fri, 31 Oct 2025 00:00:00 GMT

Automated pre-transfusion testing provides significant improvements in efficiency and productivity along with a reduction of the potential for errors. With reflex test capability and bidirectional Laboratory Information System interfacing, enhanced levels of effectiveness can be achieved in delivery of test results. To improve efficiency and productivity in our laboratory related to antibody identification (AbID) on our automated testing analyzer, we conducted a study that would allow for extended on-board utilization of our AbID reagent red blood cells (RRBCs). Our current process requires loading the 0.8 percent AbID RRBC panel onto the analyzer at the time of antibody detection and then removing and returning it to refrigerated storage once the AbID test has been completed. Our study was conducted at two hospital sites with an initial pilot study to determine the feasibility of using the RRBC panel on board with evaporation caps over a 7-day timeframe upon initial use of the panel and at two different timeframes later in the panel shelf life. Once the initial pilot study was completed and the feasibility of use established, a secondary study was initiated to determine if stability of reactivity was maintained using a rotational approach of time on board the analyzer compared with time in standard refrigerated storage. A 12-hour rotation at hospital 1 over a 2-week period and a 24-hour rotation at hospital 2 over a 3-week period were evaluated. Anti-c and anti-Fya were used at one site while the other site used anti-E and anti-K. Respective negative controls were tested at both sites. Results of the pilot study demonstrated that the reactivity of the antibodies tested over the 7-day timeframe was maintained along with antibody specificity. The secondary study demonstrated sustained reactivity strength when using the rotational approach but showed occasional yet inconsistent results with respect to specific RRBC deterioration, fibrin in patient’s plasma, or indeterminate occurrence. Based on the results of the study, a 7-day on-board utilization protocol was established for routine use. The new extended on-board protocol offers enhanced performance, efficiency, and safety for our transfusion medicine operations.

Kell and Kx blood group systems: an update

Fri, 31 Oct 2025 00:00:00 GMT

This review updates knowledge on the Kell (International Society of Blood Transfusion [ISBT] 006) and Kx (ISBT 019) blood group systems since the last review published in Immunohematology in 2015. It highlights new insights into the relationship between Kell glycoprotein and red blood cell (RBC) membrane stability, including recent discoveries of new antigens and alleles, and reporting of the first diagnosis of McLeod syndrome in an infant. The Kell and Kx blood group systems welcome an increasing number of antigens and/or alleles to their systems. Kell has a total of 38 antigens as of January 2025; a further 25 novel alleles encode Kmod phenotypes, and an additional 71 nucleotide changes are associated with the K0 (null) phenotype. XK follows a similar theme with an ever-increasing number of new alleles, all encoding the Kx– (null) phenotype. The review emphasizes the role of molecular diagnostics in resolving serologic ambiguities in the blood bank or assisting the diagnosis of neurodegenerative syndromes. The monitoring and management of anti-K in pregnancy is evolving. Emerging technologies such as single-cell sequencing and multi-omics analysis workflows, gene editing, and cellular therapeutics may unlock the inner workings of Kell and Kx protein mechanics and elucidate the function of Kell protein biology, structural immunogenicity, and explain why alloanti-K is capable of suppressing erythroid growth.

Investigation of unexplained reactivity: antibody of unknown specificity (AUS)

Tue, 08 Jul 2025 00:00:00 GMT

When antibody screening results are positive in a patient”s sample, the next step is to identify the specificity of the antibody and plan for transfusion or treatment needs. Most often, the antibody can be identified at the transfusing facility; samples that are not resolved may be referred to an immunohematology reference laboratory. A portion of these referred samples may still not be resolved, and the antibodies in these cases have been termed “antibodies of unidentified or undetermined specificity”. In this publication, we selected the term “unknown” for such antibodies. Local medical staff should be involved in the clinical management and transfusion recommendations for these patients. The flow charts described in this article are designed to guide the serologist through steps that may result in a defined antibody specificity, or they may not resolve the specificity, and thus, the antibody remains an “antibody of unknown specificity”.

The utility of an acid elution when a direct antiglobulin test is positive due to complement alone

Tue, 08 Jul 2025 00:00:00 GMT

Acid elutions are intended to recover IgG antibodies from the red blood cell (RBC) surface. Eluates from samples that are direct antiglobulin test (DAT) positive with complement (C3) only would be expected to be negative. However, elution studies performed on RBCs that are DAT positive with C3 only can produce clinically significant results. Identifying how often clinically relevant information is obtained when elutions are performed on samples DAT positive with C3 alone would aid in developing guidelines for elution performance on these samples and reducing performance of eluates on such samples with clinically insignificant results. Patient samples that are DAT positive with C3 only submitted over an 11.5-month period at the American Red Cross’ Immunohematology Reference Laboratory locations were identified. The eluate result, serum result, transfusion history, and patient diagnosis were captured and analyzed. In total, 1171 samples that were DAT positive with C3 only were identified and, of those, 321 (27%) samples had an elution performed. A nonreactive eluate was the most common result. Alloantibodies were identified in 19 (6%) eluates. Panagglutination/autoantibodies was identified in 71 (22%) eluates. Informative eluates were identified as those eluates showing any alloantibody, regardless of serum results, or panagglutination/autoantibody present in the eluate but not concurrently present in the serum (n = 30,9%). Guidelines based on recent transfusion history, indicators of active hemolysis, and autoimmune reactivity concurrently in the serum should be implemented to identify clinically significant information and to reduce the number of uninformative elutions performed.

Tue, 08 Jul 2025 00:00:00 GMT

The Rh blood group system: RHD update

Tue, 08 Jul 2025 00:00:00 GMT

The Rh blood group system was last reviewed in Immunohematology in 2010 (Chou ST, Westhoff CM. The Rh and RhAG blood group systems. Immunohematology 2010;26:178–86). This update focuses on RHD, RhD structure, alterations in D expression, anti-D alloimmunization, and applications of RHD genotyping for weak and discrepant D phenotypes; identification of RHD genotypes that encode partial D phenotypes; and prevention and management of anti-D in pregnancy. Updates to the RHAG system and to RHCE and its encoded antigens are in recent or upcoming publications of Immunohematology, respectively.

Prevalence and clinical implications of unexpected red blood cell antibodies in a tertiary care hospital in Sri Lanka

Wed, 26 Mar 2025 00:00:00 GMT

Unexpected red blood cell (RBC) alloantibodies can lead to hemolytic transfusion reactions and hemolytic disease of the fetus and newborn (HDFN). Screening for these antibodies is essential to ensure transfusion safety and improve patient care. Prevalence and frequency of unexpected antibodies vary among populations, influenced by genetic and demographic factors. This study addresses the gap in data specific to University Hospital, General Sir John Kotelawala Defence University. A retrospective analysis was performed on 20,212 patients (40.74% pregnant women and 59.25% transfusion recipients) from November 2019 to August 2024, assessing the prevalence, distribution, and clinical relevance of RBC alloantibodies. The study found that 0.80 percent of patients were alloimmunized and 28.87 percent of the antibodies were clinically significant. Common antibodies included anti-Leb (27.27%) and anti-Lea (19.25%); anti-D was the most frequent among Rh antibodies. A significantly higher proportion of pregnant women were alloimmunized compared with transfusion recipients (p < 0.000). Among D– pregnant women, 5.45 percent were alloimmunized, mainly with anti-D. HDFN was identified with either maternal anti-D or anti-E. These findings emphasize the need for early antibody detection and monitoring to enhance transfusion safety, suggesting policy improvements for antibody screening in transfusion and antenatal care in Sri Lanka.

Wed, 26 Mar 2025 00:00:00 GMT

Anti-LW masquerading as anti-D in a D+ patient

Wed, 26 Mar 2025 00:00:00 GMT

LWa, LWab, LWb, and LWEM are the four main antigens of the Landsteiner–Weiner (LW) blood group system. LW expression may be weakened during pregnancy and immune dysregulation, with the subsequent appearance of anti-LW. Here, we describe a case of an elderly male patient in whom transfusion of red blood cells (RBCs) became challenging because of the presence of anti-LW. A 61-year-old male patient presented with shortness of breath and a hemoglobin level of 7.0 g/dL, requiring RBC transfusions. Serologic workup of his blood sample showed his RBCs to be group A, D+, but his serum was incompatible with several group A, D+ donor RBC units. Antibody screening showed preferential reactivity with D+ panel RBCs that was abolished when using 0.2 M dithiothreitol-treated RBCs. The patient’s serum did not react with known RBCs of Rhnull and LW(a–) phenotypes but reacted strongly with D+ and D– cord RBCs. The patient’s sample was genotyped as LW*A/A (c.299A), consistent with the LW(a+b–) phenotype. Subsequent bone marrow examination showed B-lymphoproliferative disorder. The patient required RBC transfusion support because of his underlying disease. Transfusion of group A, D– RBCs was uneventful. The expression of LW in this patient was possibly weakened by his underlying disease, leading to the development of anti-LW. No complications were seen after multiple transfusions of group A, D– RBC units.

An update on the RHAG blood group system

Wed, 26 Mar 2025 00:00:00 GMT

This update on the RHAG blood group system (ISBT 030) (Chou ST, Westhoff CM. The Rh and RhAG blood group systems. Immunohematology 2010;26:178–86) reports the addition of three new low-prevalence antigens carried on the Rh-associated glycoprotein (RhAG). Kg (previously 700045; now RHAG5) has been demonstrated to be antithetical to the previously described high-prevalence DSLK (RHAG3). Two further low-prevalence antigens (RHAG6 and RHAG7) are described, both resulting from rare missense RHAG mutations encoding amino acid changes predicted to be externally located. All three new low-prevalence antigens have been implicated in hemolytic disease of the fetus and newborn. The RHAG system now comprises six antigens, two of high prevalence and four of low prevalence, including one antithetical pair. RHAG4 has been made obsolete.

Immunohematology Feed

To contributors to the 2025 issues

Evanescence and persistence of red blood cell antibodies over time: a single-center experience

The Indian (IN 023) blood group system: an update

Cephalosporin-induced hemolytic anemia: a case study

Contents

Improving transfusion outcomes in sickle cell disease through extended red blood cell molecular matching

The second reported case of a hemolytic transfusion reaction caused by anti-Sc2: a clinical diagnosis

Contents

Loss of D expression associated with hematologic disease progression: a case report and review of the literature

Prevalence and characteristics of irregular antibodies in northern Vietnamese blood donors

Performance of 0.8 percent reagent red blood cell panels after extended on-board analyzer utilization

Kell and Kx blood group systems: an update

Investigation of unexplained reactivity: antibody of unknown specificity (AUS)

The utility of an acid elution when a direct antiglobulin test is positive due to complement alone

Contents

The Rh blood group system: RHD update

Prevalence and clinical implications of unexpected red blood cell antibodies in a tertiary care hospital in Sri Lanka

Contents

Anti-LW masquerading as anti-D in a D+ patient

An update on the RHAG blood group system