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.”
- If the ALC is low, the CD4 will usually be low (Shapiro NI 1998).
%
× 10³ cells/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 |
Literature
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