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CION Cancer Clinics
PML-RARA: the test that confirms APL | CION Cancer Clinics
The PML-RARA test looks for the faulty joined gene that causes APL. A positive result at diagnosis confirms APL and tells the team that ATRA and arsenic trioxide are the right medicines. After treatment, the same test checks that the gene can no longer be found. This page explains how the test is done, the methods, and what each result means. At CION Cancer Clinics, every leukaemia, MDS and MPN case is reviewed by our haematologist and discussed at a tumour board before a plan is agreed.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- What is the PML-RARA test, and why does it matter?
- Which tests can find PML-RARA?
- How is the PML-RARA test done?
- What do the words on a PML-RARA report mean?
- What does a result mean at each stage of treatment?
- What do people misread about the PML-RARA test?
- What can the PML-RARA test not tell you?
- Common questions about the PML-RARA test
The short answer
What is the PML-RARA test, and why does it matter?
The PML-RARA test looks for the faulty joined gene that causes APL. A positive result confirms the diagnosis. The same test is repeated after treatment to check that the faulty gene can no longer be found.
What the test is looking for
In APL, a piece of chromosome 15 and a piece of chromosome 17 swap places. The swap joins part of a gene called PML to part of a gene called RARA. This new joined gene makes a faulty protein that stops young white cells from growing up. Finding PML-RARA in blood or bone marrow cells is what separates APL from other types of acute myeloid leukaemia.
Why it decides the treatment
ATRA and arsenic trioxide work on this specific faulty protein. A positive result tells the team these medicines are the right ones. Treatment usually starts before the result, on strong suspicion, because of the bleeding risk. The result then confirms the plan or changes it.
Rare look-alikes
A very small number of people have APL-like disease with a different gene partner joined to RARA. Some of these do not respond to ATRA or arsenic in the usual way. This is one reason the confirming test matters, even when treatment has already started.
Different methods
Which tests can find PML-RARA?
Your report may name one or more of these. They answer slightly different questions, so laboratories often use more than one. CION's team coordinates these tests with accredited laboratories.
FISH
Fluorescence in situ hybridisation. Glowing probes attach to the two genes, and the lab looks for them sitting together in the cells. It can give a fairly quick answer at diagnosis.
RT-PCR
A very sensitive test that detects the joined gene's message in the cells. It also identifies which version of the join is present.
Mainly used for
- Confirming the diagnosis
- Checking for tiny traces after treatment
Karyotype
A chromosome picture that shows the t(15;17) swap and any other chromosome changes. It takes longer, because the cells have to be grown in the lab first.
Rapid screening tests
Some laboratories use a quick stain that shows the PML protein in an abnormal speckled pattern. It supports early suspicion but does not replace a genetic test.
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How is the PML-RARA test done?
The sample
At diagnosis this is usually a bone marrow sample, often with a blood sample too. The marrow is taken from the back of the hip bone with a needle, under local anaesthetic.
Sending it safely
Genetic tests are often done in a specialist laboratory. Samples need the right tube and quick transport. Ask the team where yours is going.
Waiting for the result
FISH and rapid tests can come back quickly. RT-PCR and karyotype usually take longer. Treatment carries on while you wait.
Going through the report
Ask your haematologist to explain each line, and keep a copy. Every later test will be compared against this first one.
On your report
What do the words on a PML-RARA report mean?
- Detected or positive
- The joined gene was found in the sample. At diagnosis this confirms APL.
- Not detected or negative
- The test could not find it. After treatment this is the result the team hopes for.
- bcr1, bcr2, bcr3
- The exact point where the two genes join. It helps the laboratory track the same join in later tests.
- Molecular remission
- No PML-RARA can be found even with sensitive RT-PCR, not just under the microscope.
- MRD
- Measurable residual disease: tiny amounts of leukaemia left after treatment, too few to see under a microscope.
- Sensitivity
- How small an amount the test can pick up. It varies between laboratories and methods.
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Timing matters
What does a result mean at each stage of treatment?
When the test is done
What the result usually means
At diagnosis, positive
APL confirmed, and ATRA and arsenic are the right medicines
Soon after induction, still positive
Often expected, as cells are still clearing; the team usually does not change the plan on this alone
After consolidation, negative
Molecular remission, the goal of treatment
During follow-up, turns positive again
A repeat test is arranged quickly, as it may be an early sign of relapse
Commonly believed
What do people misread about the PML-RARA test?
"It is a gene test, so our children could carry it too."
PML-RARA forms in the marrow cells during a person's life. It is not inherited and cannot be passed on. Relatives do not need to be tested for it.
"The test came back positive after the first month, so treatment has failed."
A positive result early in treatment is common and often means the cells have not fully cleared yet. The result that matters most is the one after consolidation. Ask your haematologist before drawing any conclusion.
"Negative means the APL is gone for ever, so no more tests."
Negative is excellent news. Follow-up testing still matters, because catching a return early gives the most treatment options. The schedule depends on your risk group.
"Any lab's result can be compared with any other."
Methods and sensitivity differ. Where possible, follow-up tests should go to the same laboratory, so that changes reflect the disease and not the method.
Being straight with you
What can the PML-RARA test not tell you?
The test tells you whether the faulty gene is present. It does not tell you how the bleeding risk looks today, how well a person will tolerate treatment, or what their long-term outlook is.
What the team reads it alongside
The white and platelet counts at diagnosis place APL into a risk group, and that shapes the plan more than the gene test alone. Clotting tests guide the early days. Heart, kidney and liver checks decide how medicines are given. A single report never tells the whole story.
When a test result is unclear
Occasionally a sample has too few cells, or results from different methods do not agree. The team may repeat the test or send it to another laboratory. This can feel like a delay, but it is the safe thing to do.
Where CION fits
CION does not claim to run these tests in-house. CION's haematology team reviews results, explains them, and coordinates testing and care with qualified laboratories and centres. Ask them which laboratory will handle your follow-up samples.
Questions we are asked
Common questions about the PML-RARA test
Can PML-RARA be tested on blood instead of bone marrow?
Often yes, especially when the blood has many abnormal cells. At diagnosis, a marrow sample is usually still preferred because it gives a fuller picture. For follow-up, the team may use blood, marrow or both, depending on the stage and the laboratory. Ask which sample they plan and why.
How long does the PML-RARA result take?
It depends on the method and the laboratory. Rapid tests and FISH can be quick, while RT-PCR and karyotype usually take longer, and sample transport adds time. The team does not wait for it to start treatment when APL is strongly suspected. Ask for an expected date so you know when to follow up.
What if FISH is negative but APL is still suspected?
Some joins are hidden from FISH but found by RT-PCR, and a few rare variants involve a different gene. The team will look at all results together and may send extra tests. Treatment decisions are made on the full picture, not one method.
Is the bone marrow test very painful?
The skin and bone surface are numbed first. Most people feel pressure and a short, sharp pulling feeling when the marrow is drawn out. It is over in minutes. Some centres offer mild sedation. Tell the team if you are anxious, and ask what they can offer.
How often is the test repeated after treatment?
It is usually done at the end of consolidation and then at intervals set by your risk group and the guidance your team follows. Lower-risk patients who reach molecular remission may need fewer tests. Your haematologist will give you a written schedule to keep.
Can we get the test done at a private lab to save time?
Only through your treating team. Genetic samples need the right tube, handling and a laboratory experienced with this test. Results from a lab the team does not know can be harder to interpret and compare later. Ask the team before arranging anything yourself.
Is the PML-RARA test covered by Aarogyasri or insurance?
Diagnostic tests linked to leukaemia treatment are often covered under Aarogyasri, PM-JAY, CGHS, ECHS, EHS and cashless insurance, but coverage of specific genetic tests varies and rules change. Check the current rules for your scheme. Call the helpline and we will help you check.
Does a positive result during follow-up mean relapse?
Not always. A single positive result is usually repeated quickly to confirm it. If it is confirmed, it can mean the APL is starting to return before counts change. Early detection gives more treatment options. Your haematologist will explain what happens next.
Your Haematologist
Meet CION's haematologist. One specialist for your blood report and your plan.
Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- American Cancer Society — Tests for Acute Myeloid Leukemia (AML)
- American Cancer Society — Treating Acute Promyelocytic (M3) Leukemia
- National Cancer Institute — Adult Acute Myeloid Leukemia Treatment (PDQ) - Patient Version
- Leukemia & Lymphoma Society — Acute Myeloid Leukemia (AML)
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Why APL Is Treated Before the Diagnosis Is ConfirmedWhy treatment starts before this resultAPL Maintenance and Follow-Up MonitoringHow repeat PML-RARA tests fit into follow-upRelapsed APL: What Happens NextIf a follow-up test turns positiveAPL: The Most Curable Leukaemia and the Most UrgentThe basics of APL
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