The gel test: some problems and solutions.

The gel centrifugation test (GT) is a method of transfusion serology, based on the fact that, after centrifugation, unagglutinated red blood cells (RBC) pass easily through a gel, while agglutinated RBC do not. The introduction of the GT to our blood bank transfusion routine [strictly following the manufacturer's instructions (DiaMed ID Micro Typing System)] resulted in problems with the interpretation of the results. These were overcome after the introduction of modifications, which included: (1) the systematic use of 1% RBC suspensions; (2) the use of 50 microliters of 1% RBC suspensions and 25 microliters of serum in all tests; (3) the control of all negative indirect antiglobulin tests (IAT) and direct antiglobulin tests (DAT) by the addition of 50 microliters of a 1% IgG coated RBC suspension followed by centrifugation; and (4) the systematic use of saline-suspended RBC for ABO typing in patients with positive DAT.