NOTE: Our laboratory offers multiple testing options for APL. Please see our APL overview page.
Standard RT-PCR is reserved for patients not harbouring a transcript variant amenable to monitoring via ddRT-PCR. Sensitivity of this assay has not been specifically determined and likely varies between transcript variants. RT-PCR is generally first initiated by laboratory in response to a negative ddRT-PCR test on a patient with demonstrated t(15;17). Subsequent to the formal identification of the transcript variant in question, follow-up monitoring is initiated by this method. Invariably, results are reported qualitatively as either positive or negative for the presence of the transcript variant in question.
1. Laboratory initiated reflex test in patients with demonstrated t(15;17) positive disease (diagnosis either by FISH or karyotype) and a negative ddRT-PCR test.
2. Follow-up test for monitoring of minimal residual disease (or measurable residual disease).
The following testing interval applies to follow-up testing:
- Uncomplicated, patients treated with an ATRA/ATO based therapy.
- Every three months. Ending three years post completion of all planned therapy
- At the discretion of the treating physician, testing may be carried out after Induction and each of the consolidation phases.
- Post-transplant patients not being specifically treated for APL.
- Monitoring is at the discretion of the treating physician though it is anticipated that monitoring would not continue indefinitely.
- For any scenario not covered above, please contact the laboratory in order to come to a mutually agreeable testing interval.
Any treating physician.
- Completed CGL Myeloid Testing requisition form
- One of the following specimens (please see our Specimen Guidelines, RNA Molecular test type)
- 20mL Peripheral Blood in EDTA tubes (purple top)
- 2.5mL Bone marrow aspirate in EDTA tubes (purple top)
- Peripheral blood derived white blood cells fixed in methanol/acetic acid (residual cytogenetic specimen)
- Bone marrow specimen fixed in methanol/acetic acid (residual cytogenetic specimen)
Figure1: Requisition entries for RT-PCR testing of APL patients. Note that RT-PCR is not a routinely orderable test at diagnosis.
Total RNA is extracted from the submitted specimen and converted to cDNA (random primed reverse transcription) for subsequent PCR. Both the PML::RARA and ABL1 RT-PCR products are visualized (and sized) via electrophoresis (TapeStation) and reported qualitatively (e.g. Positive, Negative, etc).
At diagnosis, RT-PCR positivity is equivalent to the identification of t(15;17) by FISH. Subsequent MRD monitoring will follow the breakpoint identified by this test.
Results are reported within ten working days from receipt of specimen and completed requisition form.