Nonhemolytic passenger lymphocyte syndrome.

BACKGROUND: An 8-month-old recipient of a liver segment transplant had anti-D detected for the first time in her Day 5 posttransplant plasma and anti-C detected for the first time in her Day 55 posttransplant plasma. The donor's plasma contained anti-C and anti-D. Clinical and laboratory findings established a diagnosis of passenger lymphocyte syndrome (PLS). Hemolysis did not occur, because the recipient's blood group phenotype was, by chance, D- C-. STUDY DESIGN AND METHODS: To evaluate contemporary practice for diagnosing PLS, we conducted a retrospective 10-year literature review. RESULTS: There were 31 studies (63 cases) of PLS of which eight cases (four studies) were hematopoietic stem cell and 55 (27 studies) were organ transplants. All eight (100%) hematopoietic stem cell and 52 (95%) organ transplants were associated with hemolysis. Of the four studies of hematopoietic stem cell PLS, three actively screened for posttransplant blood group antibodies. Of 27 studies of organ PLS, one actively screened for antibodies. Antibody screens detected five cases of hematopoietic stem cell PLS before hemolysis was apparent and two cases of organ PLS with antibodies without hemolysis. CONCLUSION: Focusing on hemolysis, without a comparable effort to detect donor-derived antibodies diverts from the primary pathophysiology of PLS and limits capturing the full scope of the syndrome. Recognition of hemolytic and nonhemolytic subcategories of PLS is recommended. When feasible, an antibody screen performed on the donor's plasma when collecting the hematopoietic stem cells or before an organ harvest could result in an alert that the donor has formed an alloantibody(s) and the recipient is a risk for PLS. Alternatively, a routine antibody screen performed on the recipient's plasma 1 week posttransplant and, if negative, repeated 3 to 5 weeks posttransplant would detect any donor-derived antibodies and improve alignment of clinical practice with the pathophysiology of PLS.

A Guide to Terminology for Rh Immunoprophylaxis.

Rh immunoprophylaxis for Rh-negative women requires an understanding of terminology used for Rh blood typing laboratory reports. The pathophysiology of Rh hemolytic disease of the fetus and newborn was elucidated by studies in rhesus monkeys. Subsequent studies revealed that the human blood group antigen responsible for Rh hemolytic disease of the newborn (D antigen) is related to, but different from, the rhesus monkey antigen. Weak expression of the D antigen on red cells, originally termed D, is currently reported by laboratories as a "serologic weak D phenotype," which can be further defined by RHD genotyping to be either a weak D type or a partial D phenotype. Weak D types 1, 2, or 3 are molecularly defined RHD weak D types, which have an adequate number of intact D antigens to be managed safely as Rh-positive. Partial D phenotypes result from mutations causing loss of one or more D epitopes. Most persons with a partial D phenotype have sufficient D antigen to type as Rh-positive. Some women with a partial D phenotype are detected as serologic weak D phenotypes by routine Rh typing. Whether they type as Rh-positive or serologic weak D phenotype, after being exposed to Rh-positive red cells by transfusion or pregnancy, women with partial D phenotype can form anti-D antibodies and, if they do, are at risk for hemolytic disease of the fetus and newborn. A pregnant woman with a laboratory report of a serologic weak D phenotype should be further tested for her RHD genotype to resolve whether her case should be managed as Rh-positive or Rh-negative. For more than five decades, the practice of Rh immunoprophylaxis has remained unchanged in terms of the dose of Rh immune globulin and timing of injections. In contrast, advances in the science of Rh blood typing have resulted in a continuously evolving terminology, obliging obstetricians to update their vocabulary to guide their practice. The following review and glossary provide guidance for current Rh terminology and the rationale for changes.

Serological weak D phenotypes: a review and guidance for interpreting the RhD blood type using the RHD genotype.

Approximately 0·2-1% of routine RhD blood typings result in a "serological weak D phenotype." For more than 50 years, serological weak D phenotypes have been managed by policies to protect RhD-negative women of child-bearing potential from exposure to weak D antigens. Typically, blood donors with a serological weak D phenotype have been managed as RhD-positive, in contrast to transfusion recipients and pregnant women, who have been managed as RhD-negative. Most serological weak D phenotypes in Caucasians express molecularly defined weak D types 1, 2 or 3 and can be managed safely as RhD-positive, eliminating unnecessary injections of Rh immune globulin and conserving limited supplies of RhD-negative RBCs. If laboratories in the UK, Ireland and other European countries validated the use of potent anti-D reagents to result in weak D types 1, 2 and 3 typing initially as RhD-positive, such laboratory results would not require further testing. When serological weak D phenotypes are detected, laboratories should complete RhD testing by determining RHD genotypes (internally or by referral). Individuals with a serological weak D phenotype should be managed as RhD-positive or RhD-negative, according to their RHD genotype.

A model for integrating molecular-based testing in transfusion services.

BACKGROUND: Molecular-based laboratory tests can predict blood group antigens and supplement serological methods, adding a unique technology to assist in resolving discrepant or incomplete blood group typing or antibody identification. Hospital transfusion services have options for integrating molecular-based methods in their routine operations. We describe here the model of a hospital-reference laboratory partnership. MATERIALS AND METHODS: Blood samples for compatibility testing were obtained from patients in a 609-bed hospital serving an urban multiethnic and multiracial population. When results of blood group phenotyping by serological methods were inconclusive, samples were referred for molecular-based testing. The reference laboratory used several methods for genotyping, including polymerase chain reaction followed by restriction enzyme-linked polymorphism analysis, sequence-specific primer polymerase chain reaction and array-based approaches. Human erythrocyte antigen, RHCE and RHD single nucleotide polymorphism arrays were integrated into the laboratory as they became commercially available. RESULTS: The hospital-reference laboratory model made it possible to integrate blood group genotyping promptly by current technology without the expense of new laboratory equipment or adding personnel with technical expertise. We describe ten cases that illustrate the categories of serological problems that were resolved by molecular methods. DISCUSSION: In-hospital molecular testing for transfusion services has logistical advantages, but is financially impractical for most hospitals. Our model demonstrates the advantages of a hospital-reference laboratory partnership. In conclusion, hospital transfusion services can integrate molecular-based testing in their routine services without delay by establishing a partnership with a molecular blood group reference laboratory. The hospital reference-laboratory model promotes genomic medicine without the expense of new equipment and skilled personnel, while supporting the economy of centralised large-scale laboratory operations.

Rh Immunoprophylaxis for Women With a Serologic Weak D Phenotype.

It is standard practice for pregnant RhD-negative women who have not already formed anti-D to receive antepartum Rh immunoprophylaxis and, if they deliver an RhD-positive neonate, to receive postpartum Rh immunoprophylaxis. An estimated 0.6% to 1.0% of white women have red blood cells that express a serologic weak D phenotype. Of these women, approximately 80% will have a weak D type 1, 2, or 3 that could be managed safely as RhD-positive. Surveys of laboratory practice reveal a lack of standards for interpreting the RhD type for women with a serologic weak D and for determining their need for Rh immunoprophylaxis. RhD genotyping is recommended to determine the molecular basis of serologic weak D phenotypes in pregnant women as a basis for determining their candidacy for Rh immunoprophylaxis.

Financial implications of RHD genotyping of pregnant women with a serologic weak D phenotype.

BACKGROUND: Hemolytic disease of the fetus and newborn, classically caused by maternal-fetal incompatibility of the Rh blood group D antigen, can be prevented by RhIG prophylaxis. While prophylactic practices for pregnant women with serologic weak D phenotypes vary widely, RHD genotyping could provide clear guidance for management. This analysis evaluated the financial implications of using RHD genotyping to guide RhIG prophylaxis among pregnant females. STUDY DESIGN AND METHODS: A Markov-based model was constructed to evaluate the costs of RHD genotyping for pregnant females with serologic weak D phenotypes to inform RhIG prophylaxis. Using a comparison strategy of managing these women conservatively as D-, direct medical costs were assessed over 10- and 20-year periods for a simulated population of US women. One-way and probabilistic sensitivity analyses were used to assess the robustness of conclusions. RESULTS: Using base-case variables, RHD genotyping for pregnant women with serologic weak D phenotypes is expected to marginally reduce overall costs. RHD genotyping these patients, rather than conservatively managing them as D-, would be cost-saving when the cost of genotyping is below $256. Genotyping would decrease net costs among non-Hispanic Caucasian females (-$0.17/pregnancy), but would increase costs among non-Hispanic African Americans (+$0.51/pregnancy), non-Hispanic American Indian/Alaskans (+$0.10/pregnancy), and Hispanics (+$0.37/pregnancy). Incorporating RHD genotyping would not significantly impact costs among Asians and Hawaiians/Pacific Islanders. CONCLUSIONS: Using RHD genotyping to guide RhIG prophylaxis among pregnant women with serologic weak D phenotypes may be clinically beneficial without increasing overall costs.

Policies and procedures related to testing for weak D phenotypes and administration of Rh immune globulin: results and recommendations related to supplemental questions in the Comprehensive Transfusion Medicine survey of the College of American Pathologists.

CONTEXT: Advances in RHD genotyping offer an opportunity to update policies and practices for testing weak D phenotypes and administration of Rh immune globulin to postpartum women. OBJECTIVES: To repeat questions from a 1999 College of American Pathologists proficiency test survey, to evaluate current practices for testing for weak D and administration of Rh immune globulin, and to determine whether there is an opportunity to begin integrating RHD genotyping in laboratory practice. DESIGN: The College of American Pathologists Transfusion Medicine Resource Committee sent questions from the 1999 survey to laboratories that participated in the 2012 proficiency test survey. The results of the 2012 survey were compared with those from 1999. Results from published RHD genotyping studies were analyzed to determine if RHD genotyping could improve current policies and practices for serological Rh typing. RESULTS: More than 3100 survey participants responded to the 2012 questions. The most significant finding was a decrease in the number of transfusion services performing a serological weak D test on patients as a strategy to manage those with a weak D as Rh negative (from 58.2% to 19.8%, P < .001). Data from RHD genotyping studies indicate that approximately 95% of women with a serological weak D could be managed safely and more logically as Rh positive. CONCLUSIONS: Selective integration of RHD genotyping policies and practices could improve the accuracy of Rh typing results, reduce unnecessary administration of Rh immune globulin in women with a weak D, and decrease transfusion of Rh-negative red blood cells in most recipients with a serological weak D phenotype.

Postpartum Rh immunoprophylaxis.

The postpartum dose of Rh immune globulin varies according to an individual laboratory estimation of fetal red blood cells in each mother's peripheral blood. In the United States, a four-step procedure determines the postpartum dose (number of vials of 300 micrograms; 1,500 international units) of Rh immune globulin (anti-D) for each RhD-negative mother who has delivered an RhD-positive newborn and has not already formed anti-D. The first step is a rosette fetal red blood cell screen to determine whether an excessive (greater than 30 mL fetal whole blood) fetomaternal hemorrhage occurred. If the rosette screen is negative, the mother receives one vial of Rh immune globulin for Rh immunoprophylaxis. If the rosette screen is positive, the blood sample is retested by a quantitative method, typically an acid-elution (Kleihauer-Betke) assay. The result of the acid-elution assay is converted to an estimation of the volume of the fetomaternal hemorrhage, which is the basis for calculating the dose of Rh immune globulin. The acid-elution assay is subjective, imprecise, and poorly reproducible. As a result, the formula for calculating the dose includes a precautionary adjustment, adding an extra vial in borderline situations to prevent underdosing. Flow cytometry is a more precise method for quantifying a fetomaternal hemorrhage. However, few hospitals use flow cytometry, because it is not cost-effective to maintain an expensive, high-technology laboratory service for the relatively few occasions when a precise quantitative determination of fetomaternal hemorrhage is required.

New laboratory procedures and Rh blood type changes in a pregnant woman.

BACKGROUND: A woman's candidacy for Rh immune globulin depends on whether her blood type is Rh-positive (D antigen-positive) or Rh-negative (D antigen-negative). New molecular blood-typing methods have identified variant D antigens, which may be reported as Rh-positive or Rh-negative depending on the laboratory method. We describe a case illustrating the effect of the new laboratory methods on a woman's candidacy for Rh immune globulin and present recommendations for interpreting the new test results. CASE: A 40-year-old woman presented for management of her third pregnancy. During her first pregnancy, she was typed as Rh-positive ("D") and did not receive Rh immune globulin. During her second pregnancy, she was typed as Rh-negative, in accordance with revised Rh-typing procedures. Anti-D antibody was detected. During her third pregnancy, she was genotyped as a partial D antigen, which was reported as Rh-negative. CONCLUSION: Revisions in laboratory procedures for Rh typing may present as a change in the Rh blood type of pregnant women-and as a change in their eligibility for Rh immune globulin.