Intended for healthcare professionals

Practice Rational testing

Investigating an incidental finding of lymphopenia

BMJ 2014; 348 doi: (Published 03 March 2014) Cite this as: BMJ 2014;348:g1721
  1. Dawn Brass, specialty trainee in haematology1,
  2. Pam Mckay, consultant haematologist2,
  3. Fiona Scott, consultant haematologist3
  1. 1Department of Haematology Ninewells Hospital, Dundee, UK
  2. 2Department of Haematology, Beatson Oncology Centre, Gartnaval General Hospital, Glasgow, UK
  3. 3Department of Haematology, Western General Hospital, Edinburgh EH4 2XU, UK
  1. Correspondence to: F Scott fiona.m.scott{at}

Learning points

  • Lymphopenia is a common finding from a full blood count, especially in elderly patients, where it is usually of no clinical significance. No further investigation is advised in an elderly patient with a lymphocyte count >0.5×109/L in the absence of any concerning symptoms

  • Most cases are reversible and do not require specialist evaluation. The lymphopenia may reflect a response to stress such as acute infection or recent surgery or be iatrogenic secondary to medication, especially immunosuppressant drugs such as steroids

  • Symptomatic patients with persistent lymphopenia should be referred to the most appropriate specialty based on clinical and laboratory features

  • In those with unexplained moderate to severe lymphopenia (lymphocyte count <1×109/L) offer HIV testing

  • Persistent lymphopenia that remains stable over a six month period and in the absence of symptoms, clinical findings, or abnormal results from investigations does not require further investigation

A 55 year old man had a full blood count undertaken when he presented with fatigue. There was no significant medical history of note. He was a non-smoker who took no medications. He was noted to have a lymphopenia of 0.8×109/L (reference interval 1.5-4.0×109/L). Otherwise his results were normal, with haemoglobin of 135 g/L (130-180 g/L), white cell count 4.2×109/L (4-12×109/L), and platelet count 150×109/L (140-400×109/L). He did not return for follow-up but presented to a local hospital emergency department six months later with a short history of increasing breathlessness. He was diagnosed with a severe bacterial pneumonia, from which he recovered after prolonged therapy with intravenous antibiotics. His lymphocyte count during admission ranged between 0.5 and 1.0×109/L.

What should be the next investigation?

Lymphopenia and its causes

T lymphocytes make up most (60-80%) of the total peripheral …

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