Oh, Baby, Baby!! A Case Study

Case:

A 29-year-old female presented to her obstetrician’s office for a routine 16-week checkup. Routine prenatal blood work was ordered, which included a type and screen. The hospital had no prior record of the patient and proceeded with routine testing. The patient typed O, Rh positive with a positive antibody screen using column agglutination testing (gel). The hospital requested an antibody identification from the American Red Cross Immunohematology Reference Lab (IRL) in Omaha, Nebraska. The hospital reported to the IRL that the patient had never been transfused and was currently only taking prenatal vitamins.

Results:

Initial serological testing performed by the IRL indicated the patient was O, Rh positive with a broadly reactive antibody screen. The strength varied from w+ to 1+ with all cells tested at the indirect antiglobulin test (IAT) phase using polyethylene glycol (PEG) and IgG antihuman globulin (AHG). Reactivity was not observed at the immediate spin or 37°C phase of testing. An autocontrol was performed and was nonreactive at all phases of testing. A direct antiglobulin test (DAT) was performed with polyspecific AHG and was also nonreactive.

Testing was also performed using 0.2M dithiothreitol (DTT) treated reagent cells. Reactivity was observed w+ to 1+ with all DTT-treated cells at PEG/IgG. Additional testing included treating reagent cells with ficin and testing at 37°C and IAT. Similar reactions of w+ to 1+ were observed at ficin-IAT. The results of the chemical modification testing revealed that the antibody was resistant to treatment with ficin and 0.2M DTT.

A patient phenotype was performed, the patient tested C+, E+, c+, e+, K-, Fy(a+b-), Jk(a-, b+), M+, S+, s+. Three phenotypically similar cells were tested with the following results:

One cell was nonreactive, and two cells were reactive w+ to 1+. Antibodies to P1, Le^a, and Lu^a were excluded using one negative cell. Using the patient’s phenotype as a guide for exclusion, the two reactive cells suggested the possible presence of Anti-Le^b or anti-Lu^b.

The patient’s sample was tested with a Le(b-) and Lu(b+) red cell and a Le(b+) and Lu(b-) red cell:

Test results suggested the presence of anti-Lu^b.

Additional testing was performed and all other common alloantibodies to major blood group antigens were excluded at PEG/IAT. Anti-Lu^b was confirmed with a second antigen positive reagent red blood cell. The patient’s red cells were tested with anti-Lu^b antisera, and the patient typed Lu(b) antigen negative.

Titrations were performed on this sample to establish a baseline level. Titration studies tested at 60-minute incubation with no enhancement (saline) and read at IAT determined the current titer was two.

Conclusion:

Anti-Lu^b has been associated with hemolytic disease of the fetus and newborn. Antigen typing of the biological father could assist in predicting the fetus’ phenotype. Titers are recommended monthly during the first two trimesters and biweekly during the third trimester.

Should the patient need transfusion, ABO/Rh compatible units that are antigen negative for Lu(b) should be selected. Lu(b-) units are considered rare, and the assistance of the American Rare Donor Program may be needed to obtain units.

Additional Information:

The Lu(b) antigen is present on 99.8% of all populations. It is normally resistant to ficin or papain treatment and shows variable sensitivity to 0.2M DTT treatment. The antigen is weakly expressed on cord red blood cells.

Anti-Lu^b can cause mild to moderate hemolytic transfusion reactions and mild hemolytic disease of the fetus and newborn. Generally, an IgG class immunoglobulin, anti-Lu^b can also present as IgM. If the antibody is IgG, it can cross the placenta.

Reference:

Reid, Marion E., et al. The Blood Group Antigen FactsBook. Elsevier/AP, 2012.

Thank you to the Midwest Region Immunohematology Reference Lab for providing the case study.