Dx of hemolytic anemia involves the use of labs such as the corrected retic count, LDH, indirect bilirubin, blood smear, and haptoglobin. The combination of an elevated LDH and a haptoglobin < 25 is 90% specific for the presence of hemolysis while the combination of a normal LDH and a hapt > 25 is 92% specific for ruling out hemolysis. Blood smears will typically show spherocytes and the retic count should be elevated. Cases in which the retic count may be inappropriately low in the setting of AIHA include parvovirus infections, low folate or iron states, or drug suppression of the marrow.

Tests for determining the type of AIHA include the following…

1. Direct Coomb's test-the pt's RBC's are washed of adherent proteins. They are then reacted with anti-serum or monoclonal ab against IgG and a C3 fragment. If either is present on the RBC surface, agglutination will be seen.
   
2. Indirect Coomb's test- the pt's serum is incubated with nl RBC's to determine the presence of ab directed against nl cells. This test is useful mainly with checking for blood compatibility.

• usually associated with IgM ab directed against polysaccharide Ag on RBC surface. Ab "activated" in setting of colder temps which occur in the less circulated body parts (fingers, toes, nose, etc..).
• etiology of this is typically an infection such as mono or Mycoplasma although it can occur in setting of Listeria or a viral infection. Other causes include neoplastic growth of a single immunocyte clone such as in CLL, Waldenstrom's, etc…
• dx via + Coomb's test usually against ant-C3 (usually negative vs anti-IgG)
• severe hemolysis is uncommon with this as phagocytes and cytotoxic cells do not have receptors for IgM. Most destruction of cells is compliment mediated and occurs in the setting of colder temps
• tx involves supportive care and avoidance of cold temps. Steroids or splenectomy are typically not helpful unless the patient has ant-IgG cold agglutinins, which is very rare.

• typically due to IgG ab reacting with protein ag on the RBC surface at body temps. Rarely IgM can do this.
• etiology is usually drugs, autoimmune disorders, viral infections, or malignancies such as CLL.
• dx via Coomb's test positivity against IgG at room temps
• tx options include steroids, splenectomy, avoidance of precipitating agent, tx of underlying dz, etc…. With steroids, prednisone can be started at a dose of 1mg/kg/d equivalent. Once Hgb is stable the dose can be reduced to 60mg/d for over 1wk then rapidly taper to 20mg/d over 2 wks. Steroids can continue to be weaned over then next few months and then discontinued only if the Coomb's test becomes negative. If it does not then a maintenance dose of 10mg/d should be used.