Lab Test: CD4 Count, Cell Surface Immunophenotyping Level
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- 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).
- 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
- 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).
- 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.
- 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.
- 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.
- Green top tube (containing sodium heparin)
- Lavender top tube (containing ethylene diamine tetraacetic acid)
- 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.
- 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.
- 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.
Description
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Related Tests
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Test Tube Needed
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