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Practice Rational Testing

Incidental finding of lymphocytosis in an asymptomatic patient

BMJ 2009; 338 doi: (Published 10 June 2009) Cite this as: BMJ 2009;338:b2119
  1. Carolyn S Grove, haematology specialist registrar,
  2. George A Follows, consultant haematologist,
  3. Wendy N Erber, consultant haematologist
  1. 1Haematology Department, Addenbrooke’s Hospital, Cambridge CB2 0QQ
  1. Correspondence to: W N Erber wendy.erber{at}

    What tests are needed when an asymptomatic patient presents with lymphocytosis?

    The patient

    A 63 year old asymptomatic man presented for health assessment. He had no medical history and was not taking any drugs. No abnormality was found on physical examination. A blood count showed haemoglobin 126 g/l (normal range 130-180 g/l), mean corpuscular volume 87 fl (80-100 fl), platelets 160×109/l (150-400×109/l), and leucocytes 13.1×109/l (4-13×109/l) with a neutrophil count of 5.4×109/l (2-8×109/l) and lymphocytes 8.0×109/l (1-4×109/l). Blood film showed lymphocytosis, with small mature lymphocytes and “smear” cells. The red cells were normochromic and normocytic, and the platelets appeared normal.

    What should be the next investigation?

    Repeat blood count and film in 2-4 weeks

    The reporting haematologist recommended a repeat blood count and film in 2-4 weeks. This showed persistence of mild normocytic anaemia (haemoglobin 128 g/l) and lymphocytosis (8.2×109/l) of small mature lymphocytes and smear cells.

    Further investigation of normocytic anaemia

    As the mild anaemia was persistent it needed to be investigated further. A normocytic anaemia may be caused by reduced marrow erythropoiesis (due to anaemia of chronic disease or bone marrow infiltration, for example), increased red cell destruction (haemolytic anaemia), or blood loss. Appropriate investigations are a reticulocyte count, which is a surrogate measure of marrow erythropoiesis, and iron studies (ferritin, serum iron, and total iron binding capacity) to determine whether the anaemia is due to an underlying chronic disease process or iron deficiency. The red cell morphology and mean corpuscular volume (MCV) did not suggest haemolytic anaemia or megaloblastic anaemia, so tests of haemolysis (direct antiglobulin test, bilirubin, lactate dehydrogenase, haptoglobins) and vitamin B12 or folate assays were not needed.

    Lymphocyte morphology

    The morphology of the lymphocytes can help differentiate between neoplastic (primary) and reactive (secondary) lymphocytoses (box). In …

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