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Eeva-RiittaSavolainen

Leucocytosis

Essentials

Diagnose a severe infection as the cause of leucocytosis immediately and arrange treatment without delay.
Absence of leucocytosis does not rule out severe infection or malignant haematological disease.
If the cause of leucocytosis is not apparent, order further investigations considered necessary.

Starting points

Leucocytosis refers to an elevation of the total number of white cells in blood. This can be caused by a rise in the absolute or relative amount of one or more leucocyte types.
- Neutrophilia
- Lymphocytosis
- Monocytosis
- Eosinophilia
- Basophilia
Leucocytosis may be associated with
- infections and inflammations
- medication (e.g. glucocorticoids)
- physical or emotional strain
- malignant haematological disease.

Reference intervals

See table T1.

Reference ranges (mean ± 2 SD or 95%) for white cell parameters

Patients	Leucocytes (× 10⁹ /l)	Differential (%)	Absolute number (× 10⁹ /l)
Adults	3.4 -8.2
Neutrophils		35-72	1.6-6.3
Lymphocytes		18-52	1.2-3.5
Monocytes		4-12	0.2-0.8
Eosinophils		1-6	0.01-0.40
Basophils		0-1	0.00-0.09
Children
Newborn	9.0-38.0
1-2 weeks	5.0-21.0
3-4 weeks	5.0-19.5
1 month-1 year	6.0-17.5
2-6 years	5.0-14.0
7-12 years	4.5-13.5
>12 years	4.5-13.0

Leucocyte count may be increased during pregnancy, physical activity, psychological stress, meals and smoking. The leucocyte count is lower in the morning than in the afternoon. The reference ranges may slightly differ between laboratories.
Approach If the clinical picture explains the occurrence and extent of leucocytosis, no specific investigations are required. If there is no apparent cause for leucocytosis, differential leucocyte count is performed. Neutrophilia The most common form of leucocytosis An acute or chronic bacterial infection is in practice the most common cause of neutrophilia. Immature granulocytes (bands; so-called left shift) and coarse granulation of neutrophils are characteristic in the acute phase. Other causes of neutrophilia include: acute bleeding trauma, surgical procedure myocardial infarction acute or chronic inflammation (e.g. gout, rheumatoid arthritis) drugs (e.g. glucocorticoids), poisonings metabolic and endocrinological diseases (renal insufficiency, diabetic ketoacidosis) myeloproliferative diseases Polycythaemia Vera (PV) Myelofibrosis (Mf) strenuous physical exertion smoking. Eosinophilia Relatively common See separate article Eosinophilia. Lymphocytosis Relatively common Lymphocytosis is usually associated with viral infections (marked in e.g. mononucleosis). Marked lymphocytosis is seen in chronic lymphocytic leukaemia Chronic Lymphocytic Leukaemia (CLL). Monocytosis Rather uncommon Monocytosis may be seen in association with chronic infections (e.g. tuberculosis), chronic inflammatory diseases (e.g. rheumatoid arthritis) and malignant haematological diseases. Basophilia Rare Basophilia is especially encountered in association with chronic myeloid leukaemia (CML) Chronic Myelogenous Leukaemia (CML). Further investigations Bone marrow examination Bone Marrow Examination is necessary if the aetiology of leucocytosis remains unknown, especially if the differential white cell count or the clinical picture raise a suspicion of haematological malignancy. The term leukaemoid reaction is used when leucocytosis and the left shift are extensive. Gene testing is used to differentiate leukaemoid reaction from chronic myeloid leukaemia Chronic Myelogenous Leukaemia (CML). If the symptoms and findings are unremarkable, follow-up of 1-2 weeks and a new leucocyte count may be the method of choice. Leucocytosis associated with infections is transient with correct therapy. Treatment is directed against the cause of leucocytosis.