Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
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    Absolute Lymphocyte Count (ALC)

    Assesses number of lymphocytes and predicts CD4 count.
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    When to Use
    Pearls/Pitfalls
    • Typically this is used in third world countries where CD4 tests are expensive or not available.
    • Frequently used in the ED setting because CD4 tests take longer to come back and need patient consent.
    • Lymphocytes include CD4, CD8, Natural Killer Cells, and a few others. CD4 is what gets attacked by HIV, and if it gets low enough, causes AIDS.
    • Sometimes the ALC is called the “Poor Man's CD4” or the “Poor Doc's CD4.”
    %
    ×10³/µL

    Result:

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    Next Steps
    Evidence
    Creator Insights

    Advice

    • In the right clinical context, consider undiagnosed HIV as a cause of low lymphocyte count.
    • Recall that many viral infections can cause leukopenia and lymphocytopenia, including but not limited to influenza, EBV, or even the common cold.

    Formula

    ALC = WBC count x 1000 x %lymphs

    Facts & Figures

    Predicted CD4 from ALC (van der Ryst E 1998)

    ALC Predicted CD4 Count
    < 1000 cells/mm3 < 200 cells/mm3
    1000 - 2000 cells/mm3 Unable to predict
    > 2000 cells/mm3 > 200 cells/mm3
    Dr. Nathan Shapiro

    About the Creator

    Nathan Shapiro, MD, is an attending physician in the Department of Emergency Medicine at Beth Israel Deaconess Medical Center. He is also a director at the Center for Vascular Biology Research and an assistant professor at Harvard Medical School. Dr. Shapiro conducts translational and clinical research with a particular focus on endothelial cell dysfunction in sepsis.

    To view Dr. Nathan Shapiro's publications, visit PubMed

    About the Creator
    Dr. Nathan Shapiro
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