How to approach haemolysis: Haemolytic anaemia for the general physician

Article Figures & Data

Table 1.

A classification system for some examples of autoimmune haemolytic anaemia

	Warm AIHA	Cold AIHA (cold agglutinins)	Mixed AIHA
Primary	IgG +/− C3 (mostly IgG)	C3/C3d (known as CHAD)	IgG + C3
Secondary	IgG +/− C3 (mostly IgG)	C3/C3d	IgG + C3
Secondary examples	Lymphoproliferative disorders	Lymphoproliferative disorders	Lymphoproliferative disorders
	(eg CLL and NHL)	(eg NHL)	(eg NHL)
	Infections (eg CMV)	Infections (eg EBV)	Autoimmune disorders (eg SLE)
	Autoimmune disorders	Autoimmune disorders
	(eg SLE)	(eg SLE)

AIHA = autoimmune haemolytic anaemia; CHAD = cold haemagglutinin disease; CLL = chronic lymphocytic leukaemia; CMV = cytomegalovirus; EBV = Epstein–Barr virus; NHL = non-Hodgkin lymphoma; SLE = systemic lupus erythematosus.

Table 2.

Summary of laboratory tests to confirm haemolysis

Test	Finding in haemolysis	Cause
Reticulocyte count	Raised	Bone marrow response to anaemia can lead to macrocytosis
Lactate dehydrogenase	Raised	Released from the breakdown of red blood cells
Unconjugated bilirubin	Raised	Increased haemoglobin breakdown
Haptoglobin	Decreased	Binds to free haemoglobin
Direct antiglobulin test	Positive in immune cases of haemolytic anaemia	Detects immunoglobulins or complement bound in vivo to red cell membranes
Blood film	May show abnormal red blood cells	Morphology dependent on the cause of haemolysis
Urinalysis for haemoglobinuria	A positive urine dipstick for blood, but microscopy negative of red blood cells	Occurs in severe acute intravascular haemolytic anaemia that exhausts haptoglobin-binding capacity; free haemoglobin is filtered by the glomerulus and haemoglobinuria occurs