Search by Outline Set Search Limits Advanced Search Back Home

Lab Test: CD4 Count, Cell Surface Immunophenotyping Level

    Lab Test
    • CD4 Count (Cell Surface Immunophenotyping)
    Description
    • This test is used to detect the progressive depletion of CD4 T lymphocytes, which is associated with an increased likelihood of clinical complications from acquired immunodeficiency syndrome (AIDS).
    Reference Range
    • T cells:  60-95%, 800-2500 cells/mL
    • T-helper (CD4) cells:  60-75%; 600-1500 cells/mL
    • T-suppressor (CD8) cells:  25-30%; 300-1000 cells/mL
    • B cells:  4-25%; 100-450 cells/mL
    • Natural killer cells:  4-30%; 75-500 cells/mL
    • CD4/CD8 ratio:  >1
    Indications & Uses
    • Test results can indicate if a patient with AIDS is at risk for developing opportunistic infections. 
    • Also used to confirm the diagnosis of acute myelocytic leukemia (AML) and to differentiate AML from acute lymphocytic leukemia (ALL).
    Clinical Application
    • All lymphocytes originate from reticulum cells in the bone marrow.  Normal hematopoietic cells undergo changes in expression of cell surface markers as they mature from stem cells into cells of a committed lineage. 
    • CD4 helper cells and CD8 cells are examples of T-lymphocytes.  CD4 counts, when combined with HIV RNA viral load testing are used to determine the time to initiate antiviral therapy.  They also can be used to monitor antiviral therapy. 
    • The three related measurements of CD4 T lymphocytes are: 
      • Total CD4 cell count, which is measured in whole blood and is the product of the WBC count, the lymphocyte differential count, and the percentage of lymphocytes that are CD4 T cells.
      • The CD4 percentage is a more accurate prognostic marker.  It measures the percentage of CD4 lymphocytes in the whole blood sample by combining immunophenotyping with flow cytometry.
      • The ratio of CD4 (t-helper) cells to CD8 (T-suppressor) cells.  It is also more reliable than the total CD4 count. 
    • Increased levels may indicate:
      • Chronic lymphocytic leukemia, B-cell lymphoma or T-cell lymphoma. 
    • Decreased levels may indicate:
      • Organ transplant patients, HIV-positive patients, or congenital immunodeficiency.  The U.S. Public Healthy Service recommends monitoring CD4 counts every 3 to 6 months for all persons infected with HIV.
    Related Tests
    • HIV serology - this test is used to detect HIV antibody or antigen in high-risk persons.
    • HIV viral load - this test is used to determine the amount of HIV viral load in the blood of an infected patient and is an accurate marker for prognosis and disease progression.
    Drug-Lab Interactions
    • Although diurnal variation is usually of no significance, it may have some impact when counts are low.  Higher counts can be expected in the late morning hours.
    • A recent viral illness can decrease total T-lymphocyte counts.
    • Nicotine and very strenuous exercise have been shown to decrease lymphocyte counts.  However, such data are not being questioned.
    • Steroids can increase lymphocyte counts.
    • Immunosuppressive drugs will decrease lymphocyte counts.
    Test Tube Needed
    • Green top tube (containing sodium heparin)
    • Lavender top tube (containing ethylene diamine tetraacetic acid)
    Procedure
    • Maintain a nonjudgmental attitude toward the patient's sexual practices. 
    • Allow the patient ample opportunity to express his or her concerns regarding the results. 
    • Record the time of day when the blood specimen is obtained.
    • Observe universal body and blood precautions.  Wear gloves when handling blood products from all patients
    • Never recap needles.  Dispose of needles and syringes in a puncture-proof container.
    • Collect a venous blood sample in a large green-top tube and another sample in a small lavender top tube. 
    • Apply pressure or a pressure dressing to the venipuncture site and assess the site for bleeding.
    Storage and Handling
    • Keep the specimen at room temperature.  Do not refrigerate.
    • The specimen must be evaluated within 24 hours. 
    • Often specimens are sent to a central laboratory.
    What To Tell Patient Before & After
    • Explain the procedure to the patient.
    • Tell the patient that no fasting or preparation is required.
    • Instruct the patient to observe the venipuncture site for infection.  Patients with AIDS or organ recipients are immunocompromised and susceptible to infection. 
    • Encourage the patient to discuss his or her concerns regarding the prognostic information that may be provided by these results.
    References
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.
    • Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014

MESH Terms & Keywords

  • CD4, Count, Cell, Surface, Immunophenotyping