The biochemical marker of lymphocytic leukaemia is –
**Core Concept**
Lymphocytic leukemia is a type of cancer characterized by the uncontrolled proliferation of lymphoid cells in the bone marrow, leading to an abnormal increase in lymphocytes. A biochemical marker is a substance that can be measured in the blood to diagnose or monitor a disease.
**Why the Correct Answer is Right**
The biochemical marker of lymphocytic leukemia is beta-2 microglobulin (β2-microglobulin). Beta-2 microglobulin is a protein that is expressed on the surface of many types of cells, including lymphocytes. Elevated levels of β2-microglobulin in the blood are associated with a poor prognosis in patients with lymphocytic leukemia. This is because β2-microglobulin is a marker of tumor burden and disease activity.
**Why Each Wrong Option is Incorrect**
* **Option A:** Lactate dehydrogenase (LDH) is an enzyme that is elevated in many types of cancer, but it is not specific to lymphocytic leukemia.
* **Option B:** Beta-hCG is a hormone that is associated with trophoblastic disease, not lymphocytic leukemia.
* **Option C:** Creatinine is a waste product that is elevated in kidney disease, not lymphocytic leukemia.
**Clinical Pearl / High-Yield Fact**
Beta-2 microglobulin is also a prognostic marker for other types of cancer, including multiple myeloma and breast cancer.
**Correct Answer:** D. Beta-2 microglobulin.