Molecular test for eosinophilia and hematological neoplasms FIP1L1::PDGFRA is a molecular test that detects the presence of a fusion gene created by the joining of parts of the FIP1L1 and PDGFRA genes. This genetic alteration is particularly associated with a rare group of myeloid/lymphoid neoplasms with eosinophilia and is especially important because its identification may directly influence treatment selection.
What is FIP1L1::PDGFRA? FIP1L1::PDGFRA is a gene fusion that is usually created by a microscopic deletion on chromosome 4q12. This alteration joins part of the FIP1L1 gene with PDGFRA, creating a tyrosine kinase protein that is continuously active. Continuous activation of this signaling pathway may lead to abnormal proliferation of hematopoietic cells, particularly cells of the eosinophilic lineage.
What is eosinophilia? Eosinophilia is an increase in the number of eosinophils in the blood. It may be caused by many different conditions, including: allergies;
Therefore, when eosinophilia is marked or unexplained, molecular evaluation may be required to look for specific genetic alterations.
When is the test recommended? The FIP1L1::PDGFRA test may be particularly important in patients with:
Guidelines for the evaluation of clonal eosinophilia recommend testing for FIP1L1::PDGFRA as one of the first-line molecular investigations in appropriate cases.
What does the test detect? The test determines whether the following is present in the analyzed sample: FIP1L1::PDGFRA fusion Positive result Indicates the presence of the FIP1L1::PDGFRA fusion. In the context of eosinophilia and other clinical/hematological findings, this supports the diagnosis of a myeloid/lymphoid neoplasm with eosinophilia and PDGFRA rearrangement.
Negative result Means that the targeted fusion was not detected by the method used. A negative result does not exclude all clonal causes of eosinophilia. If clinical suspicion persists, additional molecular or cytogenetic analyses may be required, including testing for other alterations involving PDGFRA, PDGFRB, FGFR1, JAK2, or other relevant genetic changes.
How is the test performed? FIP1L1::PDGFRA can be identified using molecular methods such as: RT-PCR Reverse Transcription Polymerase Chain Reaction Used to detect the fusion transcript in RNA.
Real-Time Quantitative PCR RQ-PCR / qPCR May be used for highly sensitive detection of the fusion and, in relevant protocols, for quantitative assessment.
FISH Fluorescence In Situ Hybridization May be used to investigate alterations involving the 4q12/PDGFRA region.
NGS Next Generation Sequencing RNA-based molecular panels may be used to identify gene fusions, including PDGFRA alterations. In suspected cases, RT-PCR/RQ-PCR using peripheral blood is an important method; FISH or other analyses may be used when additional evaluation is required.
What type of sample is used? In many cases, the test can be performed using: Peripheral blood or, depending on the clinical situation: Bone marrow. Molecular analysis of peripheral blood may be particularly useful in the initial evaluation of clonal eosinophilia.
Why is identifying FIP1L1::PDGFRA important? Identification of this fusion is not only diagnostic information. It may have direct therapeutic significance. The FIP1L1::PDGFRA fusion creates a continuously activated tyrosine kinase, and neoplasms associated with this alteration are generally highly sensitive to imatinib, a tyrosine kinase inhibitor. Therefore, identification of this alteration may help the hematologist determine an appropriate treatment strategy.
FIP1L1::PDGFRA and hypereosinophilic syndrome Hypereosinophilia does not always represent a single disease. In some patients, after reactive causes have been excluded, a genetic alteration may be identified that indicates a clonal process. FIP1L1::PDGFRA is one of the most important alterations to investigate in this context. Patients with this fusion may have a myeloid/lymphoid neoplasm associated with eosinophilia and require specialized hematological evaluation.
Is FIP1L1::PDGFRA the same as BCR::ABL1? No. Both are gene fusions that create proteins with tyrosine kinase activity, but they involve different genes and different diseases.
BCR::ABL1 Primarily associated with: Chronic Myeloid Leukemia (CML)
FIP1L1::PDGFRA Primarily associated with: Myeloid/lymphoid neoplasms with eosinophilia and PDGFRA rearrangement. Therefore, the tests have different clinical indications.
FIP1L1::PDGFRA and JAK2 In patients with eosinophilia, a negative FIP1L1::PDGFRA result does not end the molecular investigation. Depending on the hematological characteristics, the physician may test for other alterations such as:
The selection of tests depends on the hematological phenotype and clinical suspicion.
Can the test be used to monitor treatment? Yes. In FIP1L1::PDGFRA-positive patients, molecular testing may also be used during follow-up to assess the molecular response to treatment. When a quantitative method is used, changes in transcript levels over time may provide additional information about the response to treatment. Monitoring and testing intervals are determined by the hematologist and depend on the laboratory method and clinical situation.
What happens if the test is positive? A positive result should be interpreted by a hematologist together with:
If a FIP1L1::PDGFRA-associated neoplasm is confirmed, the result may have direct significance for treatment selection.
What happens if the test is negative? If FIP1L1::PDGFRA is not detected, the hematologist may continue the investigation for other causes of eosinophilia. Depending on the case, the following may be requested:
A negative FIP1L1::PDGFRA result does not necessarily mean that no hematological disease is present.
It is a molecular test that detects the FIP1L1::PDGFRA gene fusion, an important alteration in certain myeloid/lymphoid neoplasms associated with eosinophilia.
It is primarily used in the evaluation of myeloid/lymphoid neoplasms with eosinophilia and PDGFRA rearrangement, including appropriate cases of clonal eosinophilia.
It is particularly recommended when a patient has unexplained or persistent eosinophilia and there is suspicion of a clonal process.
Yes. In many cases, it can be performed using peripheral blood; in certain cases, bone marrow may also be analyzed.
RT-PCR, RQ-PCR, FISH, or NGS may be used, depending on the laboratory and the purpose of the analysis.
It indicates the presence of the FIP1L1::PDGFRA fusion and, in the appropriate clinical context, supports a neoplasm associated with PDGFRA rearrangement.
The result should be interpreted in the hematological context and should not be considered separately from other examinations. The final diagnosis is determined by the hematologist.
Because diseases associated with FIP1L1::PDGFRA are generally highly sensitive to tyrosine kinase inhibitors such as imatinib.
Yes. Other genetic alterations can cause clonal eosinophilia. Depending on the case, additional molecular or cytogenetic tests may be required.
Yes. In positive patients, molecular testing may be used to monitor the response to treatment, depending on the method used and the hematologist’s treatment plan.
