see also [[Anaemia#Haemolytic anaemia]], [[microangiopathic haemolytic anaemia|MAHA]] # haemolytic anaemia blood tests **Lab features common to all haemolytic anaemias** | lab | interpretation | | ------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | morphological RBC abnormalities | eg spherocytosis or fragmented RBCs, or [[Sickle Cell Anaemia\|sickle cells]] | | ↑ reticulocyte count | normal bone marrow responds to anaemia by ↑ production of RBCs | | ↑ LDH | - lactate dehydrogenase is an enzyme that leaks out of damaged cells, *not specific for haemolysis*<br>- nor is bilirubin | | haptoglobin | - protein responsible for iron transport<br>- *low when too much Fe to transport* (eg haemolysed RBCs → free Fe needing transport)<br>- acute phase reactant, so it can still be normal even with haemolysis | | free haemoglobin | elevated as it spills out of RBCs. can be haemoglobinuria | others: - ↑ bilirubin (unconjugated) - *schistocytes* - fragmented RBCs - from [[microangiopathic haemolytic anaemia]] including - [[Haemolytic uraemic syndrome|HUS]], [[DIC]], [[Thrombotic Thrombocytopaenic purpura|TTP]], HELLP - also seen from mechanical artificial heart valves **Lab features specific to autoimmune causes of haemolytic anaemia** | lab | interpretation | | --------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | DAT<br>(direct antiglobulin test) | - aka direct [[Coombs test]]<br>- demonstrates RBCs coated with antibody or compliment<br>- helps discriminate btwn "warm" and "cold" haemolytic anaemia<br>*warm*: caused by Abs maximally active at humane temp (usually IgG). DAT + IgG and C3d<br>*cold*: usually caused by IgM. DAT + C3d not IgG | # Causes of haemolytic anaemia - corpuscular defects - membrane defects - spherocytosis - haemoglobinopathies - thalassaemia - [[Sickle Cell Anaemia]] - enzyme defects - G6PD def - paroxysmal nocturnal haemoglobinuria - extra corpuscular - autoimmune - idiopathic (50%) - penicillins and cephalosprins - blood transfusion - SLE - rheumatoid arthritis - methyl dopa - ulcerative colitis - hepatitis - infectious mononecleosis - mycoplasma infection - lymphoma - CLL - mechanical trauma - long distance runners - mechanical heart valves **site of haemolysis** - intravascular - [[microangiopathic haemolytic anaemia|MAHA]] - chronic cold agglutinin disease - cardiac valve disease - paroxysmal nocturnal haemglobinuria - extravascular - within the reticuloendothelial system - autoimmune diseases - Rh incompatability - chronic haemolytic disorders # Autoimmune haemolytic anaemia ## Differential causes of autoimmune haemolytic anaemia | Warm haemolytic anaemia | Cold haemolytic anaemia | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------- | | - idiopathic primary <br>- viral infections (eg [[HIV]])<br>- drugs (penicillin, methyldopa<br>- lymphoproliferative disorders (CLL, lymphoma, MM, etc)<br>- SLE and rheumatoid arthritis | - post-infectious cold agglutin disease (syphilis, post-viral, mycoplasma pneumonia, EBV, VZV, CMV, adenovirus, influenza<br> | ## manage warm haemolysis - corticosteroids - splenectomy - cyclophosphamide / azathioprine - +/- IVIG ## manage cold haemolysis - avoid cold exposure - no steroids or splenectomy ## Management of autoimmune haemolysis - plasmapheresis -- fulminant acute haemolysis - rituximab -- cold haemolytic anaemia where a B-cell lymphoprliferative disorder is at fault. - eculizumab