• Leukocytes, Lymphocytes
• Lymphocytes

• Lavender top tube
• 5 mL of whole blood

The WBC count and differential are a routine part of the complete blood count (CBC) test.

Lymphocytes are agranulocytes that are further separated into B-lymphocytes (make antibodies to attack bacteria/toxins) and T-lymphocytes (responsible for cell-mediated immunity such as attacking cells infected by viruses or attacking cancerous cells).

• Leukocytes or WBCs are differentiated into 5 different types:
1. Basophils
2. Eosinophils
3. Lymphocytes
4. Monocytes
5. Neutrophils

The lymphocyte count is primarily useful in assessing viral illnesses, some atypical bacterial infections (especially pertussis) and some blood diseases.

The White Blood Cell (WBC) count and differential, which the lymphocyte count is part of, has clinical utility in:

• Evaluation of infection or inflammation
• Assist in determination of viral versus bacterial infection
• Assist in evaluation of the stage and severity of an infection
• Detect allergic response or parasitic infections (elevated eosinophils)
• Evaluation for hematologic malignancy/disorders
• Detecting and identifying various types of myelopoietic disorders
• Detecting and identifying various types of leukemia
• Evaluating bone marrow depression
• Evaluation of need for further tests, such as manual WBC differential or bone marrow biopsy
• Evaluation of drug effects, response to chemotherapy or radiation
• Evaluation of effect of cytotoxic agents
• Screening test as part of a CBC on admission to a health care facility or before surgery

Additional information:

• The interpretation of a normal, high or low result of any given WBC type requires the context of the patient's clinical condition, history and physical examination
• Specific patterns of leukocyte response are seen in various types of diseases as determined by the differential count
• The life span of leukocytes is normally 13–20 days, after which the cells are destroyed in the lymphatic system and are excreted from the body in fecal matter.

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

WBC Differential

• Lymphocytosis is the condition of increased lymphocytes. It is important that not only the differential shows increased lymphocytes, but that the absolute number of lymphocytes is increased also (>4,000 cells/mm³ in adults or >9,000 cells/mm³ in children).
• In the event of the WBC's being >30,000/mm³ with lymphocytic predominance; bone marrow disorder/malignancy should be suspected.
• WBC's>100,000/mm³ is a medical emergency and immediate hematology/oncology consultation is needed.

Conditions, which may cause lymphocytosis include:

• Pathological:
• Blood diseases
• Agranulocytosis
• Aplastic anemia
• Banti's syndrome
• Felty's syndrome
• Heavy-chain disease
• Lymphocytic leukemia (acute or chronic)
• Multiple myeloma
• Chronic inflammatory conditions - Ulcerative colitis
• Drugs which may cause lymphocytosis include:
• Aminosalicylic acid
• Cefaclor
• Cefdinir
• Ceftazidime
• Chlorambucil
• Chlorpropamide
• Dexamethasone
• Gabapentin
• Granulocyte colony-stimulating factor
• Griseofulvin
• Haloperidol
• Levodopa
• Narcotics
• Niacinamide
• Ofloxacin
• Paroxetine
• Pergolide
• Propylthiouracil
• Quazepam
• Spironolactone
• Triazolam
• Valproic acid
• Venlafaxine
• Immune diseases
• Idiopathic thrombocytopenic purpura
• Serum sickness
• Infections
• Bacterial
• Brucellosis
• Paratyphoid
• Pertussis (almost always has lymphocytosis)
• Syphilis (Secondary and congenital)
• Tuberculosis
• Typhoid
• Viral
• Adenovirus
• Chicken pox
• Coxsackievirus A or B6
• Cytomegalovirus infections
• Echovirus
• Epstein Barr Virus (Infectious mononucleosis)
• Hepatitis (all infectious types)
• Herpes Simplex
• Herpes zoster
• HTLV-1 infection
• Measles
• Mumps
• Viral pneumonia
• Others
• Giardia lamblia
• Toxoplasmosis
• Metabolic
• Addison's disease (hypoadrenalism)
• Hyperthyroidism
• Others
• Alcohol
• Smoking
• Splenomegally (granulocytes will be sequestered which results in an increased percent of WBCs in circulation being lymphocytes)
• Physiological:
• Emotional stress
• Exercise
• Menstruation
• Newborns & Infants

Conditions, which may cause decreased lymphocytes (lymphopenia), include:

• Acute infections and illnesses
• Defects of lymphatic circulation
• Disorders of intestinal mucosa
• Intestinal lymphangiectasia
• Thoracic duct drainage
• Drugs causing decrease in lymphocytes include
• Alprazolam
• Asparaginase
• Benzodiazepines
• Bupropion
• Cefdinir
• Cefpodoxime
• Ceftriaxone
• Chlorambucil
• Cyclosporine
• Dexamethasone
• Eprosartan
• Fludarabine
• Folic acid
• Furosemide
• Glucocorticoids
• Hydrocortisone
• Ibuprofen
• Irinotecan
• Levetiracetam
• Levofloxacin
• Lithium
• Mechlorethamine
• Mirtazapine
• Muromonab-cd3
• Nelfinavir
• Niacin
• Ofloxacin
• Olsalazine
• Pamidronate
• Pentostatin
• Phenytoin
• Quazepam
• Rabeprazole
• Sirolimus
• Terbinafine
• Thiamine
• Trastuzumab
• Triazolam
• Immunodeficiency syndromes
• AIDS
• Congenital defects of cell mediated immunity
• Immunosuppressive medication
• Lymphopenia may occur with elevated corticosteroids levels due to:
• ACTH
• Corticosteroid therapy
• Cushing's syndrome
• Epinephrine
• Severe debilitating diseases
• Miliary tuberculosis
• Hodgkin's disease
• Lupus erythematosus
• Terminal carcinoma
• Renal failure

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• Amar D et al. Leukocytosis and increased risk of atrial fibrillation after general thoracic surgery. Ann Thorac Surg. 2006 Sep;82(3):1057-61; discussion 1061-2.
• Behrman: Nelson Textbook of Pediatrics, 17th ed. Chapter 710.
• Falcone FH et al. The 21^st century renaissance of the basophil? Current insights into its role in allergic responses and innate immunity. Exp Dermatol. 2006 Nov;15(11):855-64.
• LabTestsOnline®. White Blood Cell Count. [Homepage on the Internet] © 2001-2006. Last reviewed on May 6, 2005. Last accessed onOctober 17, 2006. Available at URL: http://www.labtestsonline.org/understanding/analytes/wbc/#how
• Mariani M et al. Significance of total and differential leucocyte count in patients with acute myocardial infarction treated with primary coronary angioplasty. Eur Heart J. 2006 Aug 21; [Epub ahead of print]
• Sanchez-Ramon S et al. Low blood CD8+ T-lymphocytes and high circulating monocytes are predictors of HIV-1-associated progressive encephalopathy in children. Pediatrics. 2003 Feb;111(2):E168-75.
• Sezer M et al. Association of Hematological Indices with the Degree of Microvascular Injury in Patients with Acute Anterior Wall Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention. Heart 2006 Aug 29; [Epub ahead of print].
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• Vroonhof K et al. Differences in mortality on the basis of complete blood count in an unselected population at the emergency department. Lab Hematol. 2006;12(3):134-8
• http://www.med-ed.virginia.edu/courses/path/innes/wcd/leukocytosis.cfm
• http://www.med-ed.virginia.edu/courses/path/innes/wcd/leukopenia.cfm