Referred Tests
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Test ID: FLT
FLT3 Mutation Analysis, Varies
Useful For 
Suggests clinical disorders or settings where the test may be helpful
A prognostic indicator in some patients with acute myeloid leukemia
This test should not be used to monitor residual disease following treatment.
Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
The following algorithms are available in Special Instructions:
-Acute Myeloid Leukemia: Testing Algorithm
-Acute Myeloid Leukemia: Relapsed with Previous Remission Testing Algorithm
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The FMS-like tyrosine gene (FLT3) codes for a transmembrane receptor/signaling protein (FLT3) of the tyrosine kinase group. Binding of FLT3 ligand to the FLT3 receptor ultimately leads to production of proteins that cause cell growth and inhibit cell death through apoptosis. Recently, variants in FLT3 have been found in some hematopoietic neoplasms and are particularly common in adult acute myeloid leukemia (AML) with an overall incidence of approximately 20% to 30%. The highest genetic variant rates are seen in adult patients with AML and normal- or intermediate-risk cytogenetics, and patients with acute promyelocytic leukemia.
The most common FLT3 variant consists of internal tandem duplication (ITD) of DNA sequences found in exons 14 or 15. In some subgroups of adults with AML, the presence of an FLT3 ITD variant has been found to be an adverse prognostic indicator. The second most common variant is a point alteration in the codon for an aspartate residue (D835) that resides in the activation loop of the FLT3 protein. D835 alterations have been identified in approximately 7% of AML cases but, at this time, it is not clear if the presence of this alteration has any prognostic significance. It is thought that both types of FLT3 variants lead to constitutive (always present, independent of internal or external stimuli) FLT3 activation.
Identification of an FLT3 variant in AML is clinically useful, not only because of the prognostic information it provides, but also because FLT3-inhibitory drugs have shown promise as useful therapeutic agents.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
An interpretive report will be provided.
Interpretation Provides information to assist in interpretation of the test results
An interpretive report will be issued indicating whether the FLT3 internal tandem duplication (ITD), D835 alteration, or both were detected.
Variant status will be indicated as positive or negative. If ITD positive, an allelic ratio will be reported.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test is not designed for monitoring residual disease following treatment and the following should be noted: the sensitivity of the test is less than other methods designed for residual disease testing and there have been several reports of FLT3 variants being lost or gained in neoplastic cells following treatment.
Clinical Reference Recommendations for in-depth reading of a clinical nature
1. Levis M, Small D: FLT3: ITDoes matter in leukemia. Leukemia. 2003 September;17:1738-1752
2. Gilliland DG, Griffin JD: The roles of FLT3 in hematopoiesis and leukemia. Blood. 2002 September 1;100(5):1532-1542
3. He R, Devine DJ, Tu ZJ, et al: Hybridization capture-based next generation sequencing reliably detects FLT3 mutations and classifies FLT3-internal tandem duplication allelic ratio in acute myeloid leukemia: a comparative study to standard fragment analysis. Mod Pathol. 2019 August 30;33:334-343