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
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm





    Chief Complaint


    Organ System


    Patent Pending

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    Absolute Lymphocyte Count (ALC)

    Assesses number of lymphocytes and predicts CD4 count.
    When to Use
    • 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 cells/µL


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    Next Steps
    Creator Insights


    • 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.
    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