Several Canadian blood bankers have asked about the feasibility of performing a ficin panel with PEG enhancement. They want to know if there is any written documentation on this method. They also want to know if anyone has any experience using PEG in combination with commercial ficin panels to enhance reactivity of Rh and Kidd antibodies? At least one of the Canadians reports having looked without success in several reference sources (AABB Technical manual (13th edition), Applied Blood Group Serology (3rd edition), and Clinical Immunohematology - Basic Concepts and Clinical Applications). They have "heard" of the combined use of these reagents mentioned last year at the AABB convention, but have been unable to find any supporting documentation.

Before sharing this question with the full e-Network, an expert immunohematologist in Michigan was consulted. According to the Michigan blood banker, over the years his group has tried combinations of ficin-LIS, ficin-PEG and ficin-gel and found that all those methods will enhance Rh and Jk antibodies, but that one has to be cautious and run appropriate controls to detect non-specific activity. He reports that he included the ficin-LIS method in the manual "Methods in Immunohematology, ed 2"; his group has used this method prior to the popularization of PEG whenever they suspected Jk antibodies. They routinely test their acid eluates by PEG, using both untreated and ficin-treated RBCs. They also routinely test every Rh antibody by ficin-gel whenever the patient's RBC phenotype indicates they have the potential to make another Rh antibody (e.g., R1R1 patient with anti-E); they often find anti-c that is not demonstrable by gel with untreated RBCs or by ficin-tube. They presented their ficin-gel data at the 2002 ISBT meeting in Vancouver, and wrote another paper on a ficin-only C3-binding anti-C that was enhanced by ficin-LIS/PEG/gel and caused acute intravascular hemolysis of C+ RBCs. A paper in Immunohematology 1998;1459-62 describes use of gel for antibody identification, including results of test with ficin-treated RBCs and anti-IgG cards (ficin- gel gave similar results to ficin-tube). In Transfusion 2000;40(S)119, they presented the anti-C case that caused an acute DHTR. More recently (Vox Sang 2002;83(Suppl. 2)154, they presented additional findings with ficin gel. They found 4 anti-c and 2 anti-C (all in patients with anti-E) that were detected only in ficin-gel. They were able to confirm the presence of 11 Rh antibodies in sera giving inconclusive reactions in ficin-tube (5 anti-c in patients with anti-E, 2 e with known anti-C) and 4 anti-E in c+ individuals. Nonspecific findings (10 enzyme-only autoantibodies, 1 anti-HI) were seen by both ficin-tube and ficin-gel). The Michigan blood banker would anticipate similar findings in ficin-PEG, although the "no-wash" IAT of gel may aid in the detection of some low affinity Rh alloantibodies.

The following responses were received.

ADDENDA Jan. 3, 2003

1. One of the Canadian blood bankers who raised this discussion wrote to thank the e-Network for the information and references. Thus far her laboratory has also found similar results, enhancement of Jk antibodies which were not identifiable with PEG enhancement media alone or with ficin treatment of red cells alone, and the detection of anti-e in a patient with anti-C which was reacting only inconsistently with a few cells using PEG or ficin alone.

ADDENDA Jan. 10, 2003

2. A second expert immunohematologist (this one located on the West Coast) noticed that a famous immunohematologist from Michigan had already given input on this topic. The West Coast immunohematologist, however, was a little cautious in recommending a combination of PEG and enzymes, knowing their propensity for unwanted positive reactions when used by anyone other than famous immunohematologists!

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