A colleague in Saskatchewan Canada has provided the e-Network Forum with a copy of an "IMPORTANT NOTIFICATION" (pdf file) that was recently sent by Ortho-Clinical Diagnostics regarding revisions for the package inserts for the 0.8% Reagent Red Blood Cell product line which is used with the GEL Technology. The Canadian wonders what other colleagues are doing with regards to the GEL test sensitivity when using prediluted 0.8% Reagent Red Blood Cell products for antibody screening and/or antibody identification. For example, a colleague participating in the e-Network Forum discussion entitled "Methods to obtain appropriate reaction strength when performing daily reagent QC using gel cards - Addendum #4; posted Feb. 19, 2004" reported that her institution has seen a number of examples of antibodies detected with antibody screening cells that have been diluted "in-house" using a manufacturer's diluent, but which are not detected by the same manufacturer's prediluted 0.8% Reagent Red Blood Cell panel. The most frequent examples are antibodies in the Rh system. However the reporting colleague has encountered this situation with Fy and Jk antibodies as well. She states that they also take an extra step of preparing fresh dilutions from one of their backup 3% red cell suspension antibody identification panels or employing PEG as an alternate method to enhance and identify these antibodies when they are unable to do so with the prediluted panel.

The following comments have been received.

ADDENDA Jan. 16, 2006

1. A Blood Bank Supervisor in a Southern California hospital reports that her hospital recently received a correspondence from Ortho-Clinical Diagnostics (pdf file) which included an important notification regarding Ortho-Clinical Diagnostics 0.8% screening and panel cells. This notification acknowledges that Ortho-Clinical Diagnostics is aware that some weakly reactive antibodies, particularly Anti-E and Anti-K antibodies, go undetected in certain low ionic strength test systems. Ortho-Clinical Diagnostics suggests three options for their customers that use a low ionic strength system, but not all three of these options currently apply to their automated testing platform. The inquiring colleague wonders how other sites going to deal with the notification.

ADDENDA Jan. 18, 2006

2. A colleague at a Blood Center in the USA acknowledges that her blood center's experience with antibody detection testing and identification will probably be different from that of a hospital, due to different requirements for antibody detection test sensitivity and specificity. For instance, unlike the antibody screening done on potential transfusion recipients, antibody screening on blood donors can be done using pooled reagent red cells and is not intended to pick up extremely weak antibodies. Having said that, she applauds Ortho-Clinical Diagnostics for a sincere effort to identify a root cause of their antibody detection system weakness, so that they can correct it. The warning regarding the potential failure to detect weak-E and weak-Kell has been in the package insert since 2003, so that there should not be any surprises arising from the January 2006 notification letter. Her blood center is taking the approach that "process validation and trend data is the important factor in evaluating the methodology for their needs". They report having "seen" examples of weak-E that were missed in their initial evaluation; however, in-house data suggest that the root issue for their blood center laboratory was the composition of the "pool cell makeup" rather than the additive, and that missed antibodies were so weak as to have variable reactivity under most conditions. They have experience with other methods and saw limitations depending on the antibody with those as well. They have requested that the pool cell formula be changed to improve the likelihood of detecting unexpected antibodies (such as anti-E) that exhibit a 'dosing' phenomenon. She suggests that each laboratory validate their own methods and know what their performance is, understand the weaknesses and strengths of their methods, and trend ongoing performance under real-life conditions.

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