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At a glance:

  • Microcytic anaemia with normal ferritin levels may indicate an underlying genetic haemoglobinopathy, such as thalassaemia trait or sickle cell disease.
  • In affected patients, oral iron supplementation may not be necessary or beneficial.
  • Most haemoglobinopathies are autosomal recessive and, although carriers are normally well, they are at risk of having affected children depending on the carrier status of the other parent.
  • Alert! Abnormal haemoglobin (Hb) may interfere with the reliability of haemoglobin A1c (HbA1c) tests when assessing blood sugar control in diabetic patients.

Example clinical scenario

A well 27-year-old woman is unexpectedly found to have an Hb level of 110 grams per litre (g/L) with a mean corpuscular volume (MCV) of 70 femtoliter (fl). She is keen to ensure that she is fit and healthy as she is planning a pregnancy. Her repeat full blood count is similar, and her ferritin is normal at 78 nanograms per millilitre (ng/ml).

Identifying those at risk of a genetic condition

  • Individuals presenting with persistent microcytic anaemia with normal ferritin and iron studies may have an underlying haemoglobinopathy such as thalassaemia trait or sickle cell anaemia.
  • These individuals are more commonly carriers, as affected individuals usually present earlier in life and more acutely.
  • Most haemoglobinopathies are autosomal recessive and carriers are usually well, although they are at risk of having affected children depending on the carrier status of the other parent.
  • If two carriers of an autosomal recessive condition have a child together, there is a one-in-four (25%) chance of that child being affected.
  • Flags for an underlying genetic diagnosis include:
    • Mediterranean, Arabic, Asian or African ancestry (although haemoglobinopathies can occur in all ethnic groups);
    • family history of haemoglobinopathy; and
    • persistent microcytic anaemia with normal ferritin and iron studies.

What do you need to do?

  • Send samples of the patient’s blood for haemoglobin electrophoresis.
  • Confirmed carrier status for thalassaemia or a haemoglobin variant in individuals planning a pregnancy warrants a clinical genetics referral for partner testing and genetic counselling (in these patients, oral iron supplementation may not be necessary or beneficial).
  • If a benign haemoglobin condition (such as Hb C disease, Hb D disease or Hb E disease) is identified, haematological advice and/or referral to the relevant specialty is advised.
  • More rarely, sickle cell disease or beta thalassaemia may be diagnosed, requiring urgent haematological or paediatrics referral.
  • For information about how to arrange testing in Wales, Scotland or Northern Ireland, see our dedicated Knowledge Hub resource.
  • Information about patient eligibility and test indications were correct at the time of writing. When requesting a test, please refer to the National Genomic Test Directory to confirm the right test for your patient.

Resources

For clinicians

References:

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  • Last reviewed: 08/06/2023
  • Next review due: 08/06/2024
  • Authors: Dr Johanna Wong
  • Reviewers: Dr Amy Frost, Dr Asma Hamad, Dr Imran Rafi