Rh(D) immune globulin administration in pregnancy: Retrospective audit of patient safety events followed by targeted educational intervention with Bayesian analysis.

OBJECTIVES: To examine local patient safety events related to the administration of anti-Rh(D) immune globin (RhIG) during pregnancy, and to follow-up with targeted educational intervention to improve knowledge of this process. BACKGROUND: Administration RhIG is established treatment for the prevention of haemolytic disease of the foetus and newborn (HDFN). However, patient safety events in relation to its correct use continue to occur. METHODS: A retrospective audit of patient safety events related to RhIG administration during pregnancy was performed. Targeted educational intervention in the form of PowerPoint® presentation were given to nursing staff, laboratory staff and physicians and evaluated with pre- and post-tests using multiple-choice questions given immediately before and after the presentation. RESULTS: An annual incidence of 0.24% of patient safety events related to the administration of RhIG during pregnancy was found. These events were mostly in the preanalytical phase, for example mislabelled samples or samples for D-rosette/Kleihauer-Betke testing drawn from the baby, not the mother. Using Bayesian analysis, the probability of positive effect for the targeted educational intervention was 100% with a median improved score of 29%. This was compared with a control group using standard curriculum education intervention based on the current curriculum for nursing, laboratory and medical students which showed a median improved score of only 4.4%. CONCLUSIONS: Administration of RhIG during pregnancy is a multistep process involving health care professionals of several disciplines providing opportunities to enhance the curriculum for nursing, laboratory and medical students and to ensure on-going education.

Real-world experience of anti-D immunoglobulin in immune thrombocytopenia.

In developing countries, anti-D has been used in immune thrombocytopenia (ITP) as a cheaper alternative to human immunoglobulin. We aim to analyze the response and safety profile of anti-D in patients with severe ITP. A retrospective study was conducted at a tertiary care hospital in Northern India. Patients received a single intravenous infusion of 75 µg/kg anti-D. In total, 36 patients (20 females) were included in this study. The median duration from ITP diagnosis to anti-D therapy was 235 days (range 1-1613 days). Four (11.1%) patients received anti-D as an upfront treatment. The patients' platelet counts rose significantly by the end of day three and continued to be significantly high until day 30 of receiving anti-D (p ≤ 0.001). The overall response rate (ORR) by day seven was 88.89%. There was no effect of age, sex, duration of disease, prior therapy, and platelet count on the ORR. Patients were followed up for a median duration of 52 days (longest follow-up: 3080 days). Six (6/36, 16.67%) patients continued to be in remission till the last follow-up. The hemoglobin fall was statistically significant on day three and day seven (p < 0.001 and p = 0.001) and got normalized by day 30. We observed equally good ORR in mixed populations and different phases of ITP along with long-term sustained response. The study demonstrates a quick and high response rate along with good safety profile to anti-D in all forms of ITP.

Medical care or clinical research on humans? Contaminated anti-D immunoglobulin in the GDR and its consequences.

BACKGROUND: In 1978 and 1979, contaminated anti-D immunoglobulin was used in the German Democratic Republic (GDR). As a result, several thousand women were, in the end, infected with hepatitis C. These women received medical attention, part of which was research on hepatitis C. Up to now, results of the research and data are being published in international journals. It remains unclear whether the affected women were asked to be subjects of the clinical research. METHODS: The authors analyzed historical sources and conducted interviews with contemporary witnesses. RESULTS: In the GDR, these women were compulsorily treated by physicians without sufficient information about the disease, diagnostics, and therapy. If the women refused medical care, they were coerced into it by the physicians. Medical care and research were inseparable. Without the knowledge of the women and without their consent, research was carried out on the blood samples and liver biopsies acquired from them.After the German reunification, the same physicians continued to conduct research on the same group of patients. Beginning in 1990, interferon therapy was offered to the women. Parallel to the medication with interferon, studies on the effects of the therapy were carried out. In this case as well, the women were not informed about the use of collected data, nor did they agree to it. CONCLUSIONS: Physicians should clearly define the border between medical care and scientific interest. Exclusively, data obtained from studies performed correctly under ethical point of view should be accepted for publication.

Efficacy and Safety of Anti-D Immunoglobulins versus Intravenous Immunoglobulins for Immune Thrombocytopenia in Children: Systematic Review and Meta-analysis of Randomized Controlled Trials.

OBJECTIVES: To compare the efficacy and safety of intravenous immunoglobulins (IVIG) and anti-D immunoglobulin (anti-D) in pediatric immune thrombocytopenia (ITP). STUDY DESIGN: We conducted a systematic review and meta-analysis following PRISMA guidelines, including all randomized controlled trials that have assessed the efficacy and safety of anti-D and IVIG in children with ITP. We searched Medline, Embase, and Cochrane databases. Primary outcomes were the proportion of children achieving platelet count responses as defined in each study and bleeding response. Other safety outcomes included infusion reactions and hemolysis. RESULTS: Eleven studies with 558 children were included. Anti-D was significantly inferior to IVIG at increasing platelet counts, both for thresholds of >20 × 109/L at 24-72 hours (response rate ratio for anti-D vs IVIG: 0.85, 95% CI 0.78-0.94) and >50 × 109/L at 24-72 hours (response rate ratio for anti-D vs IVIG: 0.75, 95% CI 0.61-0.92). Bleeding response was assessed in 4 studies, but some heterogeneity in reporting leads to unclear conclusion. General symptoms after anti-D infusion were less frequent than after IVIG (Peto OR 0.39, 95% CI 0.25-0.62). Hemolysis was more frequent after anti-D. The overall quality of the studies was low. CONCLUSIONS: Compared with anti-D, IVIG led to a better response in terms of platelet count and may be preferred as a first-line treatment of ITP in children with acute hemorrhagic symptoms. However, the clinical significance of IVIG superiority on platelet count remains unclear.

Disease outcomes in a cohort of women in Ireland infected by hepatitis C-contaminated anti-D immunoglobulin during 1970s.

BACKGROUND & AIM: In the mid-1990s, a group of Rh negative women was diagnosed with hepatitis C virus (HCV) genotype 1b infection, following administration of contaminated anti-D immunoglobulin in 1977-79. We aimed to describe their disease history and estimate the effect of selected host and treatment factors on disease progression. METHODS: We conducted a cohort study on the women infected with HCV. Information was collected from records at seven HCV treatment centres on demographics, treatment and health outcomes up to the 31st December 2013. We calculated cumulative incidence, case fatality, and sub hazard ratios (SHR) for disease progression using competing risks regression. RESULTS: Six hundred and eighty-two patients were included in the study. Among the chronically infected patients (n=374), 35% completed interferon-based antiviral treatment; 42% of whom had a sustained virological response. At the end of 2013, 19%, 1.9%, and 4.9% of chronically infected patients had developed cirrhosis, hepatocellular carcinoma, and liver-related death, respectively, compared with 10%, 0.8%, and 2.4% at the end of 2008. At the end of 2013, 321 (86%) of the chronically infected patients remained alive, 247 (77%) of whom were still chronically infected. Factors associated with increased cirrhosis rates included high alcohol intake (aSHR=4.9 [2.5-9.5]) and diabetes mellitus (aSHR=5.0 [2.9-8.8]). CONCLUSIONS: Development of liver-related outcomes accelerated with time, with the risk of cirrhosis, hepatocellular carcinoma, and liver-related death doubling in the last five years of follow-up, particularly in women with high alcohol consumption and diabetes mellitus. We recommend that patients with chronic HCV infection be advised of the additive harmful effect of alcohol, and that data be collected on this cohort after a further five years to analyse the effect of subsequent antiviral treatment during this rapidly evolving period in HCV treatment history. LAY SUMMARY: In the mid-1990s, a group of women were diagnosed with chronic hepatitis C virus (HCV) infection following receipt of contaminated anti-D immunoglobulin between 1977 and 1979 in Ireland. Seventy-two (19%) developed cirrhosis and 18 had died from liver-related causes (5%) after 36years of infection. Disease progression accelerated in the last five years of follow-up, particularly in women with diabetes mellitus and high alcohol consumption. We recommend that patients with chronic HCV infection be advised of the additive harmful effect of high alcohol consumption.

Anti-D in a mother, hemizygous for the variant RHD*DNB gene, associated with hemolytic disease of the fetus and newborn.

BACKGROUND: Individuals with the partial D phenotype when exposed to D+ red blood cells (RBCs) carrying the epitopes they lack may develop anti-D specific for the missing epitopes. DNB is the most common partial D in Caucasians and the clinical significance for anti-D in these individuals is unknown. STUDY DESIGN AND METHODS: This article describes the serologic genotyping results and clinical manifestations in two group D+ babies of a mother presenting as group O, D+ with alloanti-D. RESULTS: The mother was hemizygous for RHD*DNB gene and sequencing confirmed a single-nucleotide change at c.1063G>A. One baby (group A, D+) displayed bilirubinemia at birth with a normal hemoglobin level. Anti-A and anti-D were eluted from the RBCs. For the next ongoing pregnancy, the anti-D titer increased from 32 to 256. On delivery the baby typed group O and anti-D was eluted from the RBCs. This baby at birth exhibited anemia, reticulocytosis, and hyperbilirubinemia requiring intensive phototherapy treatment from Day 0 to Day 9 after birth and was discharged on Day 13. Intravenous immunoglobulin was also administered. Both babies were heterozygous for RHD and RHD*DNB. CONCLUSION: The anti-D produced by this woman with partial D DNB resulted in a case of hemolytic disease of the fetus and newborn (HDFN) requiring intensive treatment in the perinatal period. Anti-D formed by women with the partial D DNB phenotype has the potential to cause HDFN where the fetus is D+. Women carrying RHD*DNB should be offered appropriate prophylactic anti-D and be transfused with D- RBCs if not already alloimmunized.

[Clinical effect of anti-D immunoglobulin in treatment of childhood immune thrombocytopenia: a Meta analysis].

OBJECTIVE: To investigate the clinical effect and safety of anti-D immunoglobulin (anti-D) in the treatment of children with newly diagnosed acute immune thrombocytopenia (ITP) through a Meta analysis. METHODS: PubMed, EMBASE, Cohrane Library, Ovid, CNKI, and Wanfang Data were searched for randomized controlled trials (RCTs) published up to April 2017. Review Manager 5.3 was used for the Meta analysis. RESULTS: Seven RCTs were included. The Meta analysis showed that after 72 hours and 7 days of treatment, the intravenous immunoglobulin (IVIG) group had a significantly higher percentage of children who achieved platelet count >20×109/L than the anti-D group (P<0.05). There were no significant differences in platelet count after 24 hours, 72 hours, and 7 days of treatment between the anti-D (50 µg/kg) group and the IVIG group (P>0.05), and there were also no significant differences in platelet count after 24 hours and 7 days of treatment between the 50 µg/kg and 75 µg/kg anti-D groups (P>0.05). The anti-D group had a significantly greater reduction in the hemoglobin level than the IVIG group after treatment, but did not need transfusion. No children in the anti-D group or the IVIG group experienced serious adverse reactions. CONCLUSIONS: Intravenous injection of anti-D may have a similar effect as IVIG in improving platelet count in children with acute ITP, but it may be slightly inferior to IVIG in the rate of platelet increase after treatment. The anti-D dose of 50 µg/kg may have a similar effect as 75 µg/kg. The recommended dose of anti-D for treatment of ITP is safe.

Interpretation of pretransfusion testing in obstetrical patients who have received antepartum Rh immunoglobulin prophylaxis.

BACKGROUND AND OBJECTIVES: Determining whether anti-D represents active or passive alloimmunization after RhIg administration is challenging. The objectives were to use antibody reaction strength to differentiate patients who may have become RhD alloimmunized during pregnancy from those manifesting passive anti-D and to investigate which methods work best for this determination. MATERIALS AND METHODS: Data were collected from patients residing in the Edmonton region of Canada, ≥18 years old, undergoing antibody screening in late pregnancy, who received 300 µg (1500 IU) of RhIg in the preceding 120 days. A total of 1106 tests were performed on 1050 blood samples from 963 patients: 640 by PEG, 156 by gel-card and 310 by solid-phase methodology. RESULTS: PEG was the least sensitive to passive anti-D, with significantly fewer positive results at ≥8 weeks after RhIg compared to the other methods. Strength of reactivity and time since RhIg injection could be used to identify patients at high risk using PEG as a 4+ reaction at any time, ≥3+ at >2 weeks, ≥2+ at >6 weeks and ≥1+ at >14 weeks. Similarly, the gel-card method thresholds were 4+ at >5 weeks, ≥3+ at >10 weeks and ≥2+ at >15 weeks. Reaction strength by solid-phase was too variable to establish useful thresholds by this method. Infant RhD status did not significantly affect results. CONCLUSION: Patients can be risk stratified for alloimmunization by anti-D reaction strength and time after RhIg administration. The PEG method was the best of those investigated, but the gel-card method can also be used.

Platelet transfusion and respecting patient D type.

PURPOSE OF REVIEW: Current guidance allows transfusing D-mismatched platelets to D negative recipients when necessitated by logistic constraints. Although the D antigen is not expressed on the platelet membrane, platelet concentrates are still labeled by their D antigen status because the platelet concentrates contain a small quantity of red blood cells. D matching is currently recommended to prevent D alloimmunization based on frequencies of D alloimmunization after transfusing platelet concentrates obtained from whole blood collections of up to 18.7%. RECENT FINDINGS: The content of red blood cells is higher in pooled platelet concentrates prepared from whole blood collections (range: 0.036-0.59 ml) than in platelet concentrates obtained from apheresis devices (range: 0.00017-0.009 ml). Large retrospective studies with long follow-up suggest that it is not possible to rule out a secondary immunization in D negative patients who developed an alloanti-D within 4 weeks after receiving the first D-mismatched platelet transfusion, and the frequency of D alloimmunization after D-mismatched platelet transfusions ranges between 0 and 7.1%. SUMMARY: Based on the reported frequencies of D alloimmunization and data from some recent large studies, we recommend administering Rh Immune Globulin, if D-mismatched platelet concentrates prepared from whole blood collections are transfused to D negative females of childbearing potential.

How we use WinRho in patients with idiopathic thrombocytopenic purpura.

Primary immune thrombocytopenia (ITP) is an autoimmune disease that affects children and adults. WinRho SDF is a D immune globulin product that is Food and Drug Administration approved for the treatment of ITP in D+ pediatric and adult patients. WinRho is a plasma-derived biologic product dispensed from blood banks. Transfusion medicine physicians serve as a resource to health care providers regarding blood component and derivative usage and, as such, should be familiar with the use of WinRho for ITP, including the dosage, administration, and contraindications. This report details the transfusion medicine consultation practice and guidelines at a tertiary care academic medical center for the usage of WinRho SDF in patients with ITP.

Management of hypersensitivity reactions to anti-D immunoglobulin preparations.

RhD immunoglobulin G (anti-D) administered to pregnant Rh(-) women prevents Rh isoimmunization. Its use has significantly reduced the incidence of haemolytic disease of the foetus and newborn previously responsible for one death in every 2200 births. In pregnancy, acute drug-induced hypersensitivity reactions including anaphylaxis can have serious deleterious effects on the mother and foetus/neonate. Women can be erroneously labelled as drug allergic as the investigation of hypersensitivity reactions in pregnancy is complex and drug challenges are usually contraindicated. We present three cases of suspected anti-D hypersensitivity clinically presenting as anaphylaxis and delayed transfusion-related reaction. We also propose a new algorithm for the investigations of such reaction. It relies on detailed history, cautious interpretation of skin tests, foetal Rh genotyping from maternal blood and, in some cases, anti-D challenges. This is not to deprive women of anti-D which might put their future pregnancies at risk.

Anti-D immunoglobulin therapy for pediatric ITP: before and after the FDA's black box warning.

In March 2010, the Food and Drug Administration (FDA) issued a black box warning for anti-D immunoglobulin (anti-D), an approved treatment for immune thrombocytopenia (ITP). It is unknown if and how clinical practice at U.S children's hospitals has since changed. We sought to describe inpatient anti-D usage, laboratory monitoring, and anti-D complications before and after the FDA warning. Using the Pediatric Health Information System, we collected data from 41 children's hospitals. There was a modest but statistically significant decrease in anti-D usage from pre-warning to post-warning. Severe complication rates were very low and did not change appreciably.

RhIG for the treatment of immune thrombocytopenia: consensus and controversy (CME).

Anti-D immune globulin (RhIG) is a front-line option in North America for the treatment of immune thrombocytopenia (ITP) in children and adults. Recently, addition of a Food and Drug Administration-mandated black box warning highlighted the risks of intravascular hemolysis, renal failure, and disseminated intravascular coagulation after anti-D infusion, prompting concern within the medical community regarding its use. A working group convened in response to this warning to prepare a consensus document regarding the safety of RhIG because there has been no increased incidence of adverse events since the initial discovery of these reactions many years ago. The efficacy of anti-D is well documented and only briefly reviewed. The estimated incidence and proposed mechanisms for the rare, major treatment-related complications are discussed, and signal detection data associated with heightened risk of acute hemolytic reactions are presented. The importance of considering host factors, given the rarity of severe reactions, is emphasized. Safety profiles of parallel treatment options are reviewed. The working group consensus is that RhIG has comparable safety and efficacy to other front-line agents for the treatment of children and adults with ITP. Safety may be further improved by careful patient selection.

Trends in anti-D immune globulin for childhood immune thrombocytopenia: usage, response rates, and adverse effects.

In 2010, the Food and Drug Administration (FDA) added a black box warning to anti-D immune globulin (Rho(D) immune globulin, anti-D) for immune thrombocytopenia (ITP) to warn of the complications related to severe hemolysis. The objective of this retrospective medical record review was to examine recent trends in anti-D use to treat ITP and rates of adverse events in a single large pediatric hematology program. Over a 7-year period, 176 (35%) of 502 ITP patients at our center received anti-D. Anti-D was the second most commonly prescribed drug for ITP from 2003 to 2010 overall and was given first most frequently (41%). Sixty-four percent of patients responded to anti-D, but 36% had adverse effects, including five patients requiring hospitalization. From 2003 to 2010, the use of anti-D as an initial therapy for ITP significantly decreased (P < 0.001). This trend preceded the 2010 FDA black box warning. In our experience, anti-D was associated with a significant number of adverse effects when used as a treatment for ITP, although none were life-threatening. Despite recent guidelines suggesting anti-D therapy for initial treatment for ITP, anti-D therapy for ITP has significantly decreased over the past 7 years.

Dermatofibrosarcoma protuberans arising at a Rho(D) immune globulin injection site.

Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue tumor arising in the dermis. It is notorious for high rates of local recurrence despite its low metastatic potential. Although the etiology is unknown, DFSP often is considered to arise within scars and at sites of prior vaccination or trauma. Clinically, DFSP can be highly variable and mimic other soft tissue proliferations. We present a case of recurrent DFSP arising at the site of a Rho(D) immune globulin (Rhlg) injection that was administered 7 years prior. We also discuss the diagnostic challenges of DFSP as well as the indolent and locally recurrent nature of the tumor. This case serves to remind dermatologists of the highly variable clinical appearance of DFSP as well as to warn against presumptive diagnoses of lesions that mimic keloids and hypertrophic scars.

Comparison of intravenous immune globulin and high dose anti-D immune globulin as initial therapy for childhood immune thrombocytopenic purpura.

This report documents our experience with intravenous immune globulin (IVIG) (1 g/kg, iv) and high-dose, anti-D immune globulin (anti-D) (75 microg/kg) as initial treatment for childhood immune thrombocytopenic purpura (ITP). The medical records of children diagnosed with ITP at a single institution between January 2003 and May 2008 were retrospectively reviewed. Participants received either IVIG or high-dose anti-D immune globulin as their initial treatment for ITP. For the 53 patients included for analysis, there was no statistical difference in efficacy between each group; however, patients who received anti-D experienced a higher rate of adverse drug reactions (ADRs), particularly chills and rigours, and 2 of 24 patients in the anti-D group developed severe anaemia requiring medical intervention. Patients who presented with mucosal bleeding had higher rates of treatment failure (32%) compared to those who presented with dry purpura (6%), regardless of treatment. Both IVIG and high-dose anti-D are effective first-line therapies for childhood ITP. However, we observed increased ADRs in the high-dose anti-D group in contrast to previously published reports. Further studies are needed to evaluate safety and premedications for high-dose anti-D and to determine the utility of using the presence of mucosal bleeding to predict treatment failure.

First Line Treatments for Newly Diagnosed Primary Immune Thrombocytopenia in Children: A Systematic Review and Network Meta-analysis.

BACKGROUND: The first-line interventions in immune thrombocytopenia (ITP) include intravenous polyclonal immunoglobulins (IVIg), corticosteroids and anti-D immunoglobulin (anti-D). OBJECTIVE: We aimed to compare the effectiveness and safety of first line treatments for newlydiagnosed primary ITP in children to increase the platelet count. METHODS: We searched MEDLINE, EMBASE, LILACS and the Cochrane Central register of Controlled Trials (CENTRAL); and included the clinical trials. We performed the statistical analysis in R. RESULTS: We included 12 studies for meta-analysis. Compared with IVIG 2g/kg, response rates were lower for prednisone 2mg/kg at 72 hours [RR 0.04 (95% CI 0.0 to 0.68)] and at 7 days [RR 0.23 (95% CI 0.08 to 0.67)]; at 48 hours, methylprednisolone 30mg/kg also showed lower response rates [RR 0.72 (95% CI 0.52 to 0.99)]. IVIG 2g/kg and 2.5g/kg had less adverse effects than Anti- D, methylprednisolone and IVIG 0.8g/kg. For rising platelet count, no statistical differences were found at 24 hours or in 7 days; at 48 hours, IVIG 2g/kg showed better results than Anti-D 75µg/kg [MD -58.84 (95% CI -87.02 to -25.66)]. After a month, platelet count with IVIG 2g/kg was higher than Anti-D 50 and 75µg/kg [-82.03 (95% CI -102.60 to -61.46) and -78.77 (95% CI -97.80 to - 59.74), respectively], but lower than methylprednisolone 50mg/kg [MD 118 (95% CI 3.88 to 232.12)]. CONCLUSION: The total platelet count rises higher in early and late phases with IVIG than Anti-D, but in long term it is higher with methylprednisolone. Additionally, IVIG causes less adverse effects than Anti-D and corticosteroids.

Effect of chronic hepatitis C virus infection on bone disease in postmenopausal women.

BACKGROUND & AIMS: Limited data are available on the contribution of chronic HCV infection to the development of bone disease in postmenopausal women. We studied whether women who acquired HCV infection through administration of HCV genotype 1b-contaminated anti-D immunoglobulin from a single source had decreased bone mineral density (BMD) or altered levels of bone turnover markers (BTMs), compared with women who spontaneously resolved infection or age-matched healthy controls. METHODS: From a cohort of postmenopausal Irish women, we compared BMD, determined by dual-energy x-ray absorptiometry, and a panel of BTMs in 20 women chronically infected with HCV (PCR(+)), 21 women who had spontaneously resolved infection (PCR(-)), and 23 age-matched healthy controls. RESULTS: Levels of BTMs and BMD were similar in PCR(+) and PCR(-) women and healthy age-matched controls. However, there was an increased frequency of fractures in PCR(+) (n = 6) compared with PCR(-) women (n = 0, P = .007). PCR(+) women with fractures were postmenopausal for a longer time (median, 15.5, range, 5-20 years vs 4.5, range, 1-20 years in PCR(+) women without fractures; P = .033), had lower BMD at the hip (0.79, range, 0.77-0.9 g/cm(2) vs 0.96, range, 0.81-1.10 g/cm(2); P = .007), and had a lower body mass index (23.7, range 21.2-28.5 kg/m(2) vs 25.6, range 22.1-36.6 kg/m(2); P = .035). There was no difference in liver disease severity or BTMs in PCR(+) women with or without fractures. CONCLUSIONS: Chronic HCV infection did not lead to discernable metabolic bone disease in postmenopausal women, but it might be a risk factor for bone fractures, so preventive measures should be introduced. To view this article's video abstract, go to the AGA's YouTube Channel.

Investigation of whether the acute hemolysis associated with Rh(o)(D) immune globulin intravenous (human) administration for treatment of immune thrombocytopenic purpura is consistent with the acute hemolytic transfusion reaction model.

BACKGROUND: Immune thrombocytopenic purpura and secondary thrombocytopenia patients treated with Rh(o)(D) immune globulin intravenous (human; anti-D IGIV) have experienced acute hemolysis, which is inconsistent with the typical presentation of extravascular hemolysis -- the presumed mechanism of action of anti-D IGIV. Although the mechanism of anti-D-IGIV-associated acute hemolysis has not been established, the onset, signs/symptoms, and complications appear consistent with the intravascular hemolysis of acute hemolytic transfusion reactions (AHTRs). In transfusion medicine, the red blood cell (RBC) antigen-antibody incompatibility(-ies) that precipitate AHTRs can be detected in vitro with compatibility testing. Under the premise that anti-D-IGIV-associated acute hemolysis results from RBC antigen-antibody-mediated complement activation, this study evaluated whether the incompatibility(-ies) could be detected in vitro with a hemolysin assay, which would support the AHTR model as the hemolytic mechanism. STUDY DESIGN AND METHODS: Seven anti-D IGIV lots were tested to determine the RBC antibody identities in those lots, including four lots that had been implicated in acute hemolytic episodes. Hemolysin assays were performed that tested each of 73 RBC specimens against each lot, including the RBCs of one patient who had experienced acute hemolysis after anti-D IGIV administration. RESULTS: Only two anti-D IGIV lots contained RBC antibodies beyond those expected. No hemolysis endpoint was observed in any of the hemolysin assays. CONCLUSION: Although the findings did not support the AHTR model, the results are reported to contribute knowledge about the mechanism of anti-D-IGIV-associated acute hemolysis and to prompt continued investigation into cause(s), prediction, and prevention of this potentially serious adverse event.