ie red cell breakdown.

Intravascular (eg disseminated intravascular coagulation) or Extravascular (eg hypersplenism)?

Immune or non-immune? Do Indirect Coombs (anti-globulin) test.

Differential:

• disseminated intravascular coagulation – eg sepsis.  Sick! Low platelets, low Hb, abnormal clotting, high inflammatory markers.
• Hypersplenism eg G6PD deficiency, storage disorders
• autoimmune haemolysis (see below)
• Hereditary spherocytosis

Autoimmune

Type of AHA is usually revealed by antibody screen as part of Direct Antiglobulin Test (DAT) – pattern of anti IgG plus anti C3. 

Basically, warm, cold or paroxysmal cold haemoglobinuria.

Can be primary, or associated with autoimmune disease (eg SLE), lymphoproliferative disorder, infection (EBV, mycoplasma), drugs. Big spleen usually suggests secondary.

Warm means haemolysis at body temperature. Cold means triggered by cold exposure – acrocyanosis (even ischaemia) can be a feature.

Titre less important than threshold temperature for activation!

Paroxysmal cold haemoglobinuria – most common autoimmune haemolytic anaemia in under 3 yrs. Post viral. NB normal platelets, no fragments on film cf HUS. It is intravascular however, unlike warm/cold, so no liver/spleen. Donath-Landsteiner antibody. Can be with localised cold exposure eg hands in cold water, even just drinking cold water!  IgG vs P antigen on RBC.  Can be associated with syphilis. Renal failure. Plasma exchange helps.