Other possible diagnostic studies in the workup for hemolytic anemia include ferritin, urine hemosiderin, and flow cytometry.

• Ferritin^[1]: Ferritin is often increased in chronic hemolytic conditions. Ferritin is a marker of total body iron. It is unknown exactly how a high ferritin level relates to hemolytic anemia, but it is known that ferritin is an acute phase reactant that is elevated in chronic conditions. In hereditary spherocytosis, for example, a small fraction of patients have ferritin levels above 500 ng/ml. In the case of anemia of chronic disease.
• Urine hemosiderin^[2]: This is a marker of intravascular hemolysis. In some cases it is useful to distinguish whether hemolysis occurs intravascularly (within blood vessels) or extravascularly (such as in the spleen). Both urine hemosiderin and LDH are more specific markers of intravascular hemolysis. Assessment of urine hemosiderin can help with the diagnostic workup of hemolytic anemia can sometimes help guide the management plan. Warm autoimmune hemolytic anemia, for example, is due to IgG antibodies binding red blood cells and causing extravascular hemolysis. The urine hemosiderin would be low in this case. This is treated with steroids. Cold agglutinin disease, on the other hand, is less likely to be associated with extravascular hemolysis so is not treated with steroids.
• Flow cytometry^[3]: Flow cytometry can be done on red blood cells to assess for paroxysmal nocturnal hemoglobinuria, or PNH, which is one cause of hemolysis. Flow cytometry assesses for cell surface markers on red blood cells. PNH is characterized by the absence of CD55 (decay accelerating factor) and CD59 (membrane inhibitor of reactive lysis), which are complement inhibitory proteins that prevent destruction of red blood cells by complement.