In haematology it is important integrate laboratory investigations to clinical presentations. A blood transfusion was requested in a young patient with macrocytic anaemia with no previous blood count information. The blood film was reviewed rapidly:
The diagnosis of a sickle cell disease was made on the basis of the blood film. Target cells may point towards HbSC (heterozygous sickle/Haemoglobin C), which also causes sickle cell disease. However target cells can also be seen in hyposplenism which is also obvious from the blood film (Howell Jolly bodies within red cells). In order to rapidly diagnose a sickle cell disorder a sickle solubility test can be performed. This can pick up sickle haemoglobin to at least 20%, so may not pick up low levels (e.g. massive transfusion, marked anaemia, babies, coexistance with HbH disease). The test is rapid so useful in an emergency setting. It does not give a % of sickle Hb and false positives can occur therefore confirmation by another method is required (e.g. HPLC).
Our patient was confirmed to have sickle cell anaemia (HbSS) and was visiting friends out of area (hence no previous information). She had not been seen at the hospital before. She’d had a number of transfusions previously but did not have any red cell alloantibodies. She was on hydroxycarbamide for recurrent chest crisis, which was the cause of the elevated MCV. Other causes may include folate deficiency (which can occur in chronic haemolysis) and reticulocytosis.
Patients with sickle cell should receive ABO, Rh and Kell matched blood, which is negative for any antigen for which the patient has antibodies to, is sickle negative (people with sickle cell trait can donate blood in the UK) and is less than two weeks old (possibly less than one week – local policy here). There is a national database in the UK in order to check if any red cell antibodies are known. It is important to fully phenotype the patient’s red cells prior to the first transfusion (this makes it easier to know what antibodies may form at a later date). If the patient has been transfused and no historical record is available then red cell genotyping can be performed.
Her inflammatory markers were elevated and CXR showed early signs of pneumonia; therefore antibiotics were commenced. The patient was given analgesia and hydrated. She was given a two unit blood transfusion and VTE prophylaxis. The next day she had clinically improved. Patients with sickle cell disorders should usually be on regular penicilin prophylaxis, folic acid and have appropriate immunisations. So it is important not to forget follow up and longer term problems.
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