Leukemoid reaction is distinguished from CML by which laboratory score?

Leukemoid reaction is distinguished from CML by which laboratory score?

• A. LAP score
• B. WBC count
• C. Philadelphia chromosome status
• D. Hemoglobin level

Answer: (A)

The key idea is using the leukocyte alkaline phosphatase (LAP) score to tell apart a reactive, non-neoplastic rise in white cells from a malignant myeloproliferative process. In a leukemoid reaction, neutrophils are actively responding to infection or stress, so their alkaline phosphatase activity is high, giving a high LAP score. In chronic myeloid leukemia, the neutrophils and other myeloid cells are malignant and functionally abnormal, often with low alkaline phosphatase activity, producing a low LAP score. This contrast helps distinguish a reactive neutrophilia from CML when the WBC count is elevated. WBC count alone isn’t definitive because both conditions can show high counts. The Philadelphia chromosome status is a genetic marker for CML, not a numeric score, and hemoglobin level doesn’t reliably differentiate the two. So the LAP score is the best laboratory feature to separate a leukemoid reaction from CML.

The key idea is using the leukocyte alkaline phosphatase (LAP) score to tell apart a reactive, non-neoplastic rise in white cells from a malignant myeloproliferative process. In a leukemoid reaction, neutrophils are actively responding to infection or stress, so their alkaline phosphatase activity is high, giving a high LAP score. In chronic myeloid leukemia, the neutrophils and other myeloid cells are malignant and functionally abnormal, often with low alkaline phosphatase activity, producing a low LAP score. This contrast helps distinguish a reactive neutrophilia from CML when the WBC count is elevated.

WBC count alone isn’t definitive because both conditions can show high counts. The Philadelphia chromosome status is a genetic marker for CML, not a numeric score, and hemoglobin level doesn’t reliably differentiate the two. So the LAP score is the best laboratory feature to separate a leukemoid reaction from CML.