Do transfusion service laboratories use a 'control' to check for spontaneous agglutination to rule out possible false positive results when performing a direct antiglobulin test (DAT) by GEL Test Technology?

A Regional Transfusion Medicine Coordinator in Alberta, Canada is interested to learn if any transfusion service laboratories use a 'control' to check for spontaneous agglutination to rule out possible false positive results when performing a direct antiglobulin test (DAT) by GEL Test Technology. She has read a GEL Test Technology reagent manufacturer's product insert, which she reports is silent on the subject. She wonders what others are doing with regards to performing controls when doing DAT testing by GEL Test Technology.

The following comments have been received.

ADDENDA Apr. 6, 2006

1. A transfusion medicine physician in Buenos Aires, Argentina reports that at his institution they use GEL Test Technology to determine ABO/Rh, to detect and identify red cell antibodies, and to perform direct antiglobulin testing. He adds that they run an inert column (e.g., buffered gel card containing no anti-IgG) to check for spontaneous agglutination. For example, when testing umbilical cord blood there is the possibility that the presence of Wharton's jelly in the sample might cause interference and a false positive test result. In such cases, a buffered gel card containing no anti-IgG is reactive, indicating spontaneous reactivity. In that case they would repeat testing using blood obtained by heel stick puncture.

Submit comments to the e-Network Forum at enetworkforum@cbbsweb.org

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

W. Tait Stevens, MD
CBBS e-Network Forum Editor & Moderator

Elizabeth M. St. Lezin, MD
CBBS e-Network Forum Associate Editor & Moderator