Beware of fibrin residues

Abstract

A 10-year-old female patient on a cardiac transplant waiting list was fitted with a mechanical heart valve due to myocarditis. Her blood type was group O+, R1R2, K-. Eighteen months earlier the patient had a positive direct antiglobulin test (DAT) and autoantibodies with anti-Ce and anti-e specificities. However, antibody screening tests and DAT were negative by DiaMed cards, when she presented to the cardiac unit. She received three R2R2, K-cross-match- compatible (DiaMed indirect antiglobulin test [IAT]) red blood cell (RBC) units. A donor heart became available within 24 hours after transfusion. She was transferred to the children's hospital with eight compatible R2R2, K-RBC units for transplantation.When the patient arrived, a new ethylenediaminetetraacetate sample was collected, and it was found that all of the transferred, selected units appeared incompatible by DiaMed IAT (see figure). As advised by the reference laboratory, the antibody screen and cross-matches were repeated by a test tube low-ionic-strength saline (LISS) IAT method. The results were negative and the patient received 8 units uneventfully.Subsequent investigations at the reference laboratory showed mixed-field reactions by DiaMed IAT (see figure) that were eliminated when the plasma was treated with thrombin. Tests were also negative by test tube methods: LISS-IAT and polybrene techniques.Fibrin residues may cause mixed-field reactivity on DiaMed IAT cards and this may result in unnecessary delays in issuing blood. This false reactivity can be overcome by repeating tests using a thrombin-treated sample or by using a test tube method.

A new reliable test for crossmatching: microplate hydrogel immunoassay technology

“…With these advantages, MGIA‐AHG T is widely used for antibody screening and crossmatching tests. However, with samples involving residual fibrinogen from serum‐based test samples or rarely marked leukocytosis, the sedimentation of RBCs is blocked, which results in false positives (Lee et al ., ; Alwar et al ., ). RBC debris in old specimens tends to float on the surface or in the gel, which also causes false positives (Li & Ma, ).…”