A normocytic anaemia with reticulocytosis and unconjugated bilirubinaemia would raise the suspicion of a haemolytic process. Examination of the peripheral blood smear may reveal many clues as to the cause of haemolysis, and feedback from a scientist/haematologist is invaluable in this regard. Haptoglobin is an acute phase protein and may be "normal" in certain cases of extravascular haemolytic anaemias. Haptoglobin is typically undetectable in intravascular haemolysis; LD can be expected to be > 1000 in intravascular haemolysis but normally not as high in extravascular haemolysis. If the DAT is negative, the next test suggested is urine-haemosiderin, which will be positive in chronic intravascular haemolysis. PNH is one of the causes of chronic intravascular haemolysis and the diagnosis can now be confirmed flow cytometrically
