Lymphocytes

What it measures

White cells of the adaptive immune system (T, B and NK cells). Counts help evaluate viral infections, immune deficiency and lymphoproliferative disorders.

Specimen and preparation

• Specimen: Whole blood (EDTA)
• Tube: Lavender top

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Viral infections (EBV, CMV, hepatitis)
• Pertussis
• Chronic lymphocytic leukemia
• Tuberculosis
• Normal finding in young children

Causes of low values

• HIV infection
• Corticosteroids or immunosuppressants
• Chemotherapy and radiation
• Acute stress or severe illness
• Congenital immunodeficiency

Method

Automated differential with smear review; flow cytometry for subsets

Good to know

Children normally have higher lymphocyte counts than adults. Reactive (atypical) lymphocytes on the film suggest infectious mononucleosis.

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