Overview
NPM1/FLT3 assays detect common AML-defining or risk-modifying mutations: NPM1 insertion variants and FLT3 internal tandem duplications or tyrosine kinase domain point mutations.
Clinical Importance
AML diagnosis classification and European LeukemiaNet-style risk stratification
Identify FLT3 for midostaurin/gilteritinib-type pathways when indicated
Specimen Requirements
- Specimen: whole blood or plasma as validated for the assay
- Tube: lavender-top K₂EDTA (preferred for many viral load and germline DNA assays)
- Handling: mix gently; separate plasma promptly when required; avoid heparin for many PCR assays (inhibition)
- Storage: refrigerate or freeze plasma per IFU; extract nucleic acid within validated windows
- Bone marrow or peripheral blood with adequate blast content as validated
Analytical Method
Fragment analysis detects FLT3-ITD size/burden; PCR/sequencing detects FLT3-TKD and NPM1 insertions. NGS myeloid panels may include these genes with orthogonal confirmation as needed. Allelic ratio for ITD is prognostically relevant when reported.
Instruments Used
Automated analyzers
- Applied Biosystems / Thermo Fisher real-time PCR systems (e.g., QuantStudio-class)
- Roche Cobas molecular / LightCycler systems
- Cepheid GeneXpert cartridge PCR systems
- BioFire FilmArray syndromic PCR systems
- Illumina next-generation sequencing platforms
- Thermo Fisher Ion Torrent sequencing platforms
- Digital PCR systems (e.g., Bio-Rad QX / QIAGEN QIAcuity-class)
- Specialized BCR-ABL quantitative PCR systems / kits
Manual methods
- Manual RNA/DNA extraction with real-time PCR or sequencing workflows
Reference Values
Molecular cutoffs, units (IU/mL, copies/mL, Ct), reportable ranges, and variant classifications are assay- and laboratory-specific. Always interpret against the performing laboratory report, manufacturer IFU, and current CLSI / CAP / AMP / ACMG guidance as adopted locally. Limit of detection and inhibition controls are essential for negative results.
Mutations reported as detected/not detected with ITD allelic ratio when applicable. Risk group assignment follows current AML guidelines with cytogenetics.
Interpretation
Common Causes of Increased Results
- NPM1 and/or FLT3 mutation detected; integrate with karyotype/NGS for ELN risk and therapy
Common Causes of Decreased Results
- Not detected; other AML drivers may still be present on broader panels
Clinical Significance
- AML molecular workup
Factors Affecting Results
Pre-analytical
- Wrong specimen type or transport medium for the validated assay
- Delayed transport degrading RNA targets
- Contamination during collection (especially amplicon-rich environments)
- Inadequate volume or low cellularity/tumor content
Analytical
- PCR inhibition (heparin, humic acids, excess hemoglobin; assay-dependent)
- Extraction failure or pipetting/contamination in amplification areas
- Probe/primer mismatch with sequence variants causing false negatives
- Calibration/QC failure; expired reagents
Post-analytical
- Reporting Ct or raw copies without assay-specific interpretive rules
- Misapplying another laboratory’s LOD or units
- Variant classification without current ACMG/AMP framework when required
Advantages and Limitations
Advantages
- Rapid, high-impact AML markers
Limitations
- Does not replace full myeloid NGS when available
- ITD ratio method-dependent
Clinical Pearls
FLT3-ITD without an allelic ratio is only half the risk story AML guidelines want.
References
Authoritative textbooks, guidelines, and reviews supporting this laboratory test reference. Verify reference intervals, critical limits, and method details against institutional protocols and current guideline editions.
Textbooks
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021. (Molecular diagnostics chapters, verify current edition.)
- Buckingham L. Molecular Diagnostics: Fundamentals, Methods, and Clinical Applications. 3rd ed. F.A. Davis; 2019. (Verify current edition and institutional adoption.)
CLSI and Professional Guidelines
- Clinical and Laboratory Standards Institute (CLSI). Consult current CLSI molecular method documents available through your laboratory, document numbers and editions change; do not treat any single CLSI title as universal.
- Institutional molecular laboratory standard operating procedures (SOPs), assay manufacturer instructions for use (IFU), and locally adopted accreditation requirements. Always verify current local practice.
- Clinical and Laboratory Standards Institute (CLSI). Molecular method evaluation and related documents (verify current CLSI editions applicable to the assay).
- College of American Pathologists. Molecular pathology accreditation and proficiency testing expectations (verify current CAP checklist requirements).
- Association for Molecular Pathology (AMP). Practice guidelines and position statements for molecular diagnostics (verify current AMP documents for the assay).
- American College of Medical Genetics and Genomics (ACMG). Standards and guidelines for interpretation of sequence variants and related genetic testing practice (verify current ACMG documents).
WHO Publications
- World Health Organization. Laboratory and diagnostic guidance relevant to molecular testing (verify current WHO publication for the assay/pathogen).
Frequently Asked Questions
Common questions about using this NPM1 / FLT3 Testing laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.
What is the NPM1 / FLT3 Testing laboratory test reference used for?
This Medical Laboratory Library page summarizes the clinical importance of NPM1 / FLT3 Testing. Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.
Where can I find NPM1 / FLT3 Testing specimen requirements?
See the Specimen Requirements section on this page for specimen information related to NPM1 / FLT3 Testing. Confirm collection details against your laboratory protocol.
Where are NPM1 / FLT3 Testing reference values listed?
See the Reference Values section on this Laboratory Library page. Reference ranges can vary by method and population, so verify intervals with your laboratory.
How do I interpret NPM1 / FLT3 Testing results?
Use the Interpretation section for laboratory interpretation framing, including increased and decreased result patterns when provided. Do not treat educational text as a patient-specific diagnosis.
What analytical method is used for NPM1 / FLT3 Testing?
See the Analytical Method section for principle and method notes. Method details may differ by instrument and institutional SOP.
Are related laboratory tests linked from NPM1 / FLT3 Testing?
Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.
How can I continue learning after reading NPM1 / FLT3 Testing?
Use Continue learning links on this page for related Academy lessons, medical laboratory quizzes, or laboratory case studies when available for this Molecular Diagnostics topic.
What are the clinical pearls for NPM1 / FLT3 Testing?
See the Clinical Pearls section for concise laboratory practice notes associated with NPM1 / FLT3 Testing. Apply pearls alongside institutional protocols.
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