Management of patients with anti-C^w in the absence of commercial anti-C^w typing reagent 

A medical director of a hospital blood bank in Missouri is reconsidering a policy on how her blood bank handles patients who have the red cell antibody 'anti-C^w' because her laboratory can no long obtain anti-C^w typing reagent commercially.  One possibility that they have considered is to limit identification of future anti-C^w antibodies to that of an antibody to a low frequency antigen, and to then rely entirely on an antiglobulin (AHG) crossmatch for selection of appropriate donor RBC units, since donor RBC units can no longer be typed for the C^w antigen.  Another proposal is to flag all patients with previously characterized anti-C^w as requiring AHG-crossmatched C antigen negative units.  They think that the only situation not covered with that protocol would be a scenario where a C^w positive, C negative donor RBC unit is selected for a recipient with undetectable C^w antibody, leading to a possible delayed immune reaction. New patients with a positive antibody screen in a pattern suggestive of anti-C^w could have their serum tested with either archived C^w positive donor samples or have the serum sent to a reference lab. The Missouri colleague would be interested to learn if others are having difficulty obtaining commercial anti-C^w and if so, what they are doing with regards to anti-C^w.

The following comments have been received.

ADDENDA Sept. 7, 2004

1. A Blood Bank Laboratory Supervisor in New England reports that AABB Blood Banks and Transfusion Services Standard 5.15.3 states "When clinically significant red cell antibodies are found or the recipient has a history of such antibodies, Whole Blood or Red Blood Cell components shall be prepared for transfusion that do not contain the corresponding antigen..." However, she points out that in her hospital it is standard practice to rely on the AHG crossmatch to determine compatibility when dealing with low frequency antibodies. Even as an AABB accredited Immunohematology Reference Lab/Transfusion Service, her institution does not routinely test units for low frequency antigens. They reserve this rare antisera for screening units for patients with multiple antibodies.

ADDENDA Sept. 8, 2004

2. A colleague in Ohio, who is a very big Buckeye fan, reports that he has been informed by manufacturers that there was only one donor available for manufacturing reagent anti-C^w, and that this donor is no longer available. The Ohio colleague suggests that if blood bankers discover a new potential donor with strong anti-C^w, that the individual be made aware of the opportunity of becoming a reagent donor. In terms of dealing with a patient with anti-C^w, he has his institution select donor RBCs for transfusion based entirely on an antiglobulin crossmatch and preserves available anti-C^w reagent for situations such as neonatal typing, in cases of suspected anti-C^w induced hemolytic disease of the newborn, although there is a case report wherein a PCR technology was used to determine fetal C^w antigen status. (See case abstract: Reiner AP, Teramura G, Aramaki KM. Use of a PCR-based assay for fetal anti-C^w antigen genotyping in a patient with a history of moderately severe hemolytic disease of the newborn due to anti-C^w. Am J Perinatol. 1999;16(6):277-81.) Anti-C^w is an uncommon cause of clinically significant hemolytic disease of the newborn (HDN). The authors report an unusually severe case of HDN due to anti-C^w that required phototherapy and exchange transfusion. They describe a novel PCR-RFLP method for C^w typing of fetal genomic DNA that was used for prenatal diagnosis in a subsequent pregnancy. Following PCR amplification of a 163 bp segment of the RHCE gene containing the nucleotide 122 G to A substitution that corresponds to the C^w allele, C^w types were distinguished by TaqI digestion. PCR-RFLP analysis confirmed that the father and previously affected child were C^w-positive. The fetus was C^w-negative, thus excluding HDN in the current pregnancy and obviating the need for further invasive or noninvasive diagnostic procedures for the remainder of the pregnancy. This case illustrates the utility of PCR-based fetal genotype determination in pregnancies at risk of HDN due to uncommon red cell antibodies such as anti-C^w.

3. A Scientific Director of a Molecular Blood Group and Platelet Antigen Laboratory in the Eastern USA reports that screening of donor units in the absence of commercial typing reagents is a major reason to consider molecular testing. She acknowledges that fewer laboratories in the US are doing this testing than in Europe, but she believes that it is an important tool to provide transfusion support.

ADDENDA Sept. 10, 2004

4. A colleague in a reference laboratory in Switzerland reports that in Europe (as well as in Switzerland) there is still a polyclonal anti-C^w available, but for several years they have also used a monoclonal anti-C^w, and have had no problems with obtaining the reagent for C^w-typing.

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator