What it is: A CD8+ T-cell count measures the number of CD8 cells (cytotoxic T-cells), another type of white blood cell, in a blood sample using flow cytometry.
Why it's ordered: Often ordered alongside a CD4 count to calculate the CD4:CD8 ratio, most commonly for monitoring HIV and immune health.
What it detects: CD8 cells directly destroy infected or abnormal cells. Comparing CD8 counts to CD4 counts (the CD4:CD8 ratio) gives a fuller picture of immune balance than either count alone, which is especially useful in tracking HIV progression and treatment response.
Collection & prep: A standard blood draw from a vein in the arm, usually paired with a CD4 count. No special preparation is required.
Results:
Normal – roughly 150 to 1,000 cells/mm³, varying by lab and individual health
Abnormal CD4:CD8 ratio – a ratio outside the typical 1.5:1 to 2.5:1 range can indicate immune dysfunction
Possible complications: An abnormal CD8 count or CD4:CD8 ratio on its own isn't diagnostic; it's interpreted alongside CD4 count, viral load, and clinical history to assess immune function.
Statements made in the Clinical Manual have not been evaluated by the FDA. The products mentioned are not intended to diagnose, treat, cure or prevent any disease.
