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FISH, APL with Reflex to RARA
Test Code34305
CPT Codes
88271 (x2), 88275
Includes
When the FISH result is negative for PML:RARA fusion and the RARA signal pattern is suspicious for a variant RARA rearrangement, then FISH, APL, RARA BA using a RARA break-apart probe will be performed at an additional charge (CPT code(s): 88271 (x2), 88275).
If results are not possible from the submitted specimen, the test order will be cancelled and replaced by non-orderable test Cytogenetics Communication.
If results are not possible from the submitted specimen, the test order will be cancelled and replaced by non-orderable test Cytogenetics Communication.
Preferred Specimen
5 mL whole blood or 3 mL bone marrow collected in sodium heparin (green-top) tube or EDTA (lavender-top) tube
Minimum Volume
Whole blood: 3 mL
Bone marrow: 1 mL
Bone marrow: 1 mL
Other Acceptable Specimens
Whole blood collected in sodium heparin (royal blue-top) tube, or sodium heparin lead-free (tan-top) tube • Bone marrow collected in sodium heparin (royal blue-top) tube, sodium heparin lead-free (tan-top) tube, or in a bone marrow transport tube (available upon request)
Instructions
Clinical history/reason for referral is required with test order. Prior therapy and transplant history should be provided with test order.
Specimen viability decreases during transit. Send specimen to testing laboratory for viability determination. Do not freeze. Do not reject.
Transport Temperature
Room temperature
Specimen Stability
Room temperature: Preferred
Refrigerated: Acceptable
Frozen: Unacceptable
Refrigerated: Acceptable
Frozen: Unacceptable
Methodology
Fluorescence In Situ Hybridization (FISH)
Setup Schedule
Set up: Daily; Report available: 5-7 days
Reference Range
See Laboratory Report
Clinical Significance
Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia with distinct clinical and histopathologic features. Historically one of the most lethal forms of acute myeloid leukemia, APL leads to disseminated intravascular coagulation and death when not diagnosed and treated. Treatment with all-trans-retinoic acid substantially improves survival in patients who have failed anthracycline chemotherapy or for whom anthracycline is contraindicated. Similarly, arsenic trioxide is beneficial in APL patients who have failed or have contraindications for treatment with anthracycline or retinoid-based therapy.
Genetically, APL is characterized by a unique chromosomal anomaly. More than 99% of APL patients harbor a translocation between chromosomes 15 and 17, which fuses the retinoic acid receptor alpha (RARA) gene on chromosome 17 with the PML gene on chromosome 15. A short or a long transcript isoform is produced, depending on the PML breakpoint; the short isoform has been linked to poor outcome, but this association remains controversial. Detection of the PML/RARA t(15;17) translocation is diagnostic for APL, although the diagnosis can also be based on morphology. The presence of this translocation is necessary for response to all-trans-retinoic acid and arsenic trioxide. Thus, the PML/RARA t(15;17) assay is useful for diagnosis and predicting treatment response. It is also helpful for monitoring therapeutic response and MRD and for detecting early relapse.
This RARA break-apart probe is useful for detecting variant RARA translocations with partners other than PML. Therefore, this testing is useful for verifying RARA status when morphology is suspicious for APL but t(15;17) FISH is negative.
Genetically, APL is characterized by a unique chromosomal anomaly. More than 99% of APL patients harbor a translocation between chromosomes 15 and 17, which fuses the retinoic acid receptor alpha (RARA) gene on chromosome 17 with the PML gene on chromosome 15. A short or a long transcript isoform is produced, depending on the PML breakpoint; the short isoform has been linked to poor outcome, but this association remains controversial. Detection of the PML/RARA t(15;17) translocation is diagnostic for APL, although the diagnosis can also be based on morphology. The presence of this translocation is necessary for response to all-trans-retinoic acid and arsenic trioxide. Thus, the PML/RARA t(15;17) assay is useful for diagnosis and predicting treatment response. It is also helpful for monitoring therapeutic response and MRD and for detecting early relapse.
This RARA break-apart probe is useful for detecting variant RARA translocations with partners other than PML. Therefore, this testing is useful for verifying RARA status when morphology is suspicious for APL but t(15;17) FISH is negative.
