W. John Judd

Molecular Genetic Analysis of the ABO Blood Group System: 1. Weak Subgroups: A3 and B3 Alleles

We have determined the nucleotide sequences of the coding region in the last two coding exom of ABO genes (which occupy 91% of the soluble form of A1 transferase) from 7 individuals with weak subgroup phenotypes. Four of the individuals had an A3 phenotype and 3 individuals had a B3 phenotype. We determined the nucleotide sequences based on PCR followed by subcloning and DNA sequencing of the amplified fragments. Two cases of the A3 allele and 1 case of the B3 allele were found to contain a single‐base substitution which resulted in an amino acid substitution. However, no other cases of A3 and B3 alleles were found to contain differences in this region. This finding demonstrates for the first time heterogeneity among these weak subgroups at the nucleotide level.

Practice guidelines for prenatal and perinatal immunohematology, revisited

In 1990, a subcommittee of the Scientific Section Coordinating Committee (SSCC) of the AABB formulated guidelines for prenatal and perinatal immunohematologic testing.1 These guidelines were published to provide transfusion service directors and supervisors with an authoritative source for reference in discouraging the use of outmoded tests and practices. Several changes have occurred in the decade since the SSCC guidelines were published. First, with the development of managed-care programs, routine testing is ordered by the primary care giver and often is performed by commercial laboratories. The extent to which hospital transfusion services need to repeat such tests for medicolegal reasons can be questioned, and there is an understandable reluctance on the part of health insurance companies to reimburse for such confirmatory testing. Second, the administration of Rh immune globulin (RhIg) prophylaxis is now often the responsibility of outpatient clinic nurse managers, rather than being under the purview of the transfusion service. Third, changes in regulations disallow reimbursement for laboratory tests not ordered by a licensed physician. Fourth, there have been changes in reagents and test methods, and considerable knowledge has been gained about the molecular basis and structure of blood group polymorphisms, especially those of the Rh blood group system. In light of these changes, it has become necessary to relax some of the previous guidelines and, in other cases, to introduce new ones. The following represents current opinions on prenatal and perinatal testing.

Rh discrepancies caused by variable reactivity of partial and weak D types with different serologic techniques

BACKGROUND: RhD discrepancies between current and historical results are problematic to resolve. The investigation of 10 discrepancies is reported here.

Requirements for the electronic crossmatch

With the integration of laboratory information systems into transfusion services, it is now possible to develop standard operating procedures (SOPs) for an electronic crossmatch (EXM) to replace the immediate‐spin crossmatch for detecting ABO incompatibility between the blood sample submitted for pre‐ transfusion testing and the donor unit selected for transfusion. Essential to the safety of an EXM are requirements that: 1) the computer contains logic to prevent assignment and release of ABO incompatible blood; 2) no clinically significant antibodies are detected in the recipients serum/plasma and there is no record of previous detection of such antibodies; 3) there are concordant results of at least two determinations of the recipients ABO type on record, one of which is from a current sample; 4) critical elements of the system have been validated on‐site; and, 5) there are mechanisms to verify the correct entry of data prior to release of blood.

THE ROLE OF LECTINS IN BLOOD GROUP SEROLOGY

Many lectins display blood group activity, and extracts from Dolichos biflorus (anti-A1), Ulex europaeus (anti-H), and Vicia graminea (anti-N) seeds provide an alternative to human sera as a source of blood-typing reagents. However, the major application of lectins in blood group serology undoubtedly lies in the recognition and elucidation of red celll polyagglutination. In this respect, lectins from Arachis hypogaea (anti-T/Tk), Salvia sclarea (anti-Tn). Salvia horminum (anti-Tn + Cad). Dolichos biflorus (anti-Tn/Cad) Glycine max, and the N-acetyl-D-glucosminyl-binding lectin, BS II (anti-Tk) from Bandeiraea simplicifolia seeds, provide an invaluable source of reagents for use in investigative immunohemotology. Because of their specific carbohydrate-binding properties, lectins have also been used as probes in studies on the topography of the red cell surface. This latter appliction has provided much information on the structure of the MN, T, and Tn red cell surface receptors and has aided in defining the red cell membrane abnormalities associated with certain uncommon phenotypes within the MN blood group system.

Persistence of cefotetan on red blood cells

BACKGROUND:  Cefotetan can cause severe immune hemolytic anemia that may persist long after the drug is discontinued. To study the binding of cefotetan to RBCs, patients who received cefotetan were followed and tested for the presence of antibody to cefotetan.

Infusion of P-Capt prion-filtered red blood cell products demonstrate acceptable in vivo viability and no evidence of neoantigen formation

BACKGROUND: Transmission of variant Creutzfeldt‐Jacob disease (vCJD) is a major concern in blood transfusion. The P‐Capt filter has been shown to remove around 4 log ID50 prion infectivity from prion‐spiked human red blood cells (RBCs).

How I manage cold agglutinins.

ararely cause accelerated destruction of mismatched red blood cells (RBCs), and it is not necessary to detect examples of these antibodies that only react below body temperatures. The extent to which cold agglutinins can interfere with the results of pretransfusion antibody detection and compatibility tests is evident from a study by Garratty 1 on the importance of anticomplement reagents in immunohematology. With a low-ionic-strength saline (LISS) method that included room temperature incubation and polyspecific (anti-IgG+ C3) antiglobulin serum, the rate of unwanted positive tests (due primarily to the detection of cold-reactive auto- and alloagglutinins) was on the order of 1.41 percent! Omitting the room temperature incubation phase and use of anti-IgG reduced the unwanted positive rate reduced to 0.1 percent.

Case report and literature review: transient Inab phenotype and an agglutinating anti-IFC in a patient with a gastrointestinal problem

BACKGROUND: The Inab phenotype is a rare deficiency of all Cromer antigens. These antigens are carried on the decay‐accelerating factor (DAF, CD55) molecule that is attached to the red blood cell (RBC) membrane by a glycosylphosphatidylinositol (GPI) anchor. Although typically inherited, an acquired and transient form of the Inab phenotype also exists. A patient with the triad of transient Inab phenotype, a direct‐agglutinating anti‐IFC, and gastrointestinal (GI) abnormalities is reported.

Revisiting the issue: can the reading for serologic reactivity following 37°C incubation be omitted?

BACKGROUND: Omitting the 37°C reading from screening tests for unexpected antibodies results in failure to detect some Rh, K, and Jk agglutinins of potential significance (wanted positives). However, this measure avoids unwanted positive tests due to cold agglutinins.