The best way to check for sickle cell trait or sickle cell disease is to look at the blood using a method called high-performance liquid chromatography (HPLC). This test identifies which type of hemoglobin is present.To confirm the results of HPLC, a genetic test may be done. These people have normal red blood cells, unless they have some other disease. 2  One gene that makes hemoglobin A and one that makes hemoglobin S. These people carry the sickle cell trait (and are called a carrier ), but they do not have sickle cell disease. 3  Sickle cell trait is usually a harmless condition.