Characteristics of Rouleaux

Stacked coin” appearance when viewed microscopically  Observed in all tests containing the patient’s serum, including the autologous control and the reverse ABO grouping.  Does not interfere with the AHG phase of testing because the patient’s serum is washed away prior to the addition of the AHG reagent.  Unlike agglutination, rouleaux is dispersed by adding one to three drops of saline to the test tube.  Confirm in the microscope