Hematology Test

Terminal Deoxynucleotidyl Transferase/ TdT/ Terminal Deoxyribonucleotidyl Transferase/ Terminal Transferase

Dr. Simi Paknikar
Medically Reviewed by Dr. Simi Paknikar, MD
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Test : Terminal Deoxynucleotidyl Transferase/ TdT/ Terminal Deoxyribonucleotidyl Transferase/ Terminal Transferase

Indications : The test is used to classify certain leukemias and lymphomas, normally used to distinguish lymphoblastic from non-lymphoblastic leukemia, diagnose acute lymphoblast leukemia, lymphoid blast crisis of chronic myelogenous leukemia, and lymphoblastic lymphomas.

Physiology : TdT acts to catalyze the polymerization of deoxynucleoside triphosphates. Thymus is the primary site of TdT positive cells and TdT is found in the nucleus of the more primitive T cells. A thymus related population of TdT positive cells resides in the bone marrow.

Normal Range : Peripheral blood is negative for TdT-positive cells, bone marrow <1.8% TdT-positive cells.>

Interpretation : TdT is increased in more than 90% of the cases of ALL of childhood. This is true for even pre-B cell as well as B-cells ALL. TdT positive blasts are prominent in some cases of chronic myelogenous leukemia relating to the development of an acute blast phase. TdT has been reported to assist in establishing the diagnosis of acute lymphoblastic leukemia. TdT positive cases of blast phase CML correlate with a positive response to chemotherapy vincristine and prednisone.

Test Method : ELISA, Indirect Immunofluorescence antibody,

Related Tests : Bone marrow, Immuno-phenotypic Analysis of Tissues, Lymph node biopsy

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