No abstract

The Rh blood group system is the next most important to the ABO system in terms of its clinical significance in blood transfusion. It is vital to the safe, efficient practice of transfusion medicine that Rh D phenotyping tests are selected, executed and interpreted correctly. However, the Rh D blood group antigen has been shown to be subject to many phenotypic variations, and different reagents and typing techniques vary in their ability to detect these variants. The range of D-positive phenotypes are reviewed in terms of their reactivity with monoclonal antibody reagents and their clinical significance. In view of the available evidence, it is suggested that patient typing can be safely achieved by the duplicate use of one high-avidity or two very similar IgM monoclonal anti-D reagents that detect most variants except category DVI in simple tube or microplate saline tests. Antiglobulin testing for weak D should not be carried out on patient samples. Donor typing can be safely achieved by the use of the same monoclonal, used in parallel with a polyclonal anti-D reagent that detects DVI on sensitive automated equipment.

A monoclonal anti-A antibody has been evaluated and found suitable for use as a potent routine ABO grouping reagent, without the use of additives. The IgM anti-A (MH2/6D4) is secreted into the tissue culture supernatant by a permanent line of cloned cells derived by fusion of anti-A producing spleen cells and a mouse myeloma cell line. This is a cost-effective reagent which should reduce production costs by over 50%. This reagent has the advantages inherent in monoclonal antibodies among them the availability of unlimited quantities of unvarying antibody of known properties.

Summary. An evaluation is given of haemolysin, neutralisation, thermostability, saline titration, anti‐Ap antibody absorption and 2‐mercapto‐ethanol studies on the sera from 178 clinically affected ABO HD cases and 130 control cases. The antiglobulin titre on the 2‐mercapto‐ethanol treated sera which determines the IgG titre was the best procedure used for the demonstration of significant immune anti‐A/B antibodies in the maternal sera. The screen series on 5,704 sera from group 0 mothers for the detection of immune anti‐A/B and the attempted prediction of ABO HD revealed that ABO HD occurs with a frequency of about 0.8%. Exchange transfusion was needed in six cases i.e. about 0.1% of all the infants of group O mothers screened. The minimum criteria for the diagnosis of ABO HD are the serological demonstration of incompatible anti‐A/B antibodies in an eluate prepared from the baby' red cells, accompanied by the clinical observation of jaundice, or more rarely pallor due to anaemia, in the infant during the first few days following birth. In the absence of elution or serum studies on a blood sample from the baby, the presence of an incompatible high titre (>256) IgG antibody in the maternal serum provides good presumptive evidence that the baby may be suffering from ABO HD.