Medical Oncologist
CION Cancer Clinics
When a genetic test fails or comes back inconclusive | CION Cancer Clinics
A failed genetic test means the laboratory could not get a reliable reading from your sample. It is not a result about your genes, good or bad. An inconclusive test produced a reading that does not yet answer the question clearly. This page explains why each one happens, what usually comes next, and the questions worth asking before anyone takes a second sample. At CION Cancer Clinics in Hyderabad, our oncologists review your family history with you and guide you to the right genetic counselling and testing.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- What does it mean when a genetic test fails?
- What usually goes wrong with the sample?
- What happens after a test fails or comes back unclear?
- The phrases a failed or unclear report uses
- Failed test or inconclusive result: how they differ
- What this page cannot tell you
- Four things families assume after a failed test
- Common questions about failed and unclear genetic tests
The short answer
What does it mean when a genetic test fails?
A failed test means the laboratory could not get a reliable reading from the sample it received. It says nothing about your genes. It is not a positive result, and it is not a negative one. Most of the time the fix is simply a fresh sample.
Failed and inconclusive are not the same thing
A failed test produced no usable answer at all. The DNA was too little, too damaged or not clearly yours, so the laboratory stopped before reporting anything. An inconclusive test did produce a reading, but part of it could not be read with confidence, or it found something the laboratory cannot yet explain. The next step is different for each, which is why it helps to know which one you have.
Why this happens more often than people expect
Genetic testing depends on a small amount of DNA surviving a long journey. A blood tube may travel from a district clinic to a laboratory in another city, sometimes in heat. A tissue block may be many years old. Every step is a chance for the sample to degrade, and laboratories would rather report nothing than report something they cannot stand behind.
A failed test is a problem with the sample, not a finding about you or your family.Why samples fail
What usually goes wrong with the sample?
Most failures fall into one of four groups. Knowing which one applies tells you whether a simple repeat will work.
Too little DNA, or damaged DNA
Blood that clotted, sat too long before posting or got too warm in transit can break down. Saliva samples fail when the tube holds too little spit or food got mixed in.
Usually fixed by
- A fresh blood or saliva sample
- Faster, cooler transport the second time
Old or treated tissue
When the relative who had cancer has died, a stored tissue block from their surgery is sometimes the only source left. The chemicals that preserve tissue also damage DNA, and older blocks fail more often.
Blood that is not only yours
After a bone marrow or stem cell transplant from a donor, the blood carries the donor's DNA. An active blood cancer can also muddy a blood sample. In both cases a small skin sample is often used instead.
Always tell the laboratory about any transplant or recent transfusion.Labelling and paperwork
A tube with a missing name, a mismatched date of birth or no signed consent form will be rejected before testing starts. This is the easiest failure to prevent and the most frustrating to repeat.
Not sure whether this applies to you?
Ask an oncologistAfter the call
What happens after a test fails or comes back unclear?
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The laboratory tells the doctor who ordered it
The report or a phone call goes to the ordering doctor or counsellor, not usually to you directly. It should say whether the test failed outright or produced a partial or unclear result.
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Someone works out why
The reason decides the next step. A clotted tube needs only a repeat. A transplant history needs a different sample type. A hard-to-read region may need a second testing method rather than a new sample.
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You are asked whether to repeat
Ask directly whether the repeat is charged again. Many laboratories repeat a failed test at no extra cost when the failure was on their side, but policies differ, so get the answer before the new sample is taken.
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A new sample, or a second method
A fresh blood tube, saliva kit or skin sample is sent. For an inconclusive region, the laboratory may run a different kind of test on the DNA it already holds.
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The result is explained properly
When a usable answer arrives, it should come with a counselling appointment, just as the first result would have. A repeat is not a reason to skip that conversation.
On your report
The phrases a failed or unclear report uses
- Sample failure
- The laboratory could not extract enough good DNA to test. No part of the test was reported.
- Quality control failure
- The test ran, but the reading did not meet the laboratory's own standard for accuracy, so it was not released.
- Low coverage
- Part of a gene was read too few times to be trusted. The report may list the regions that were not fully checked.
- Inconclusive
- A reading was produced but does not give a clear yes or no for the question that was asked.
- Variant of uncertain significance
- A spelling difference the laboratory found but cannot yet class as harmful or harmless. It is not a failed test.
- Confirmation testing
- A second, different method used to check a finding before it is reported as certain.
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Side by side
Failed test or inconclusive result: how they differ
Failed test
Inconclusive result
No reading was produced at all
A reading exists, but part of it is unclear
Usually needs a fresh sample
May need a second method, not a new sample
Says nothing at all about your genes
Says something, but not enough to act on
Should not change any medical plan
Should not change any medical plan on its own
Being straight with you
What this page cannot tell you
It cannot tell you why your particular test failed, or whether a repeat will succeed. Only the laboratory report and the person who ordered the test can answer that. What your specific result means is a question for the counsellor who ordered the test.
It cannot turn an unclear result into a clear one
If part of your report is marked inconclusive, reading about the gene online will not settle it. Some regions of some genes are hard to read because a near-identical copy sits elsewhere in the DNA. The laboratory knows which regions those are and what extra test can reach them.
Who this does not apply to
If your report gives a clear result, positive or negative, this page is not about you. The same is true if your test was on a tumour sample to guide treatment. That is a different kind of test, covered on our targeted therapy pages, and its failures have different causes.
If you are unsure whether your report is failed, unclear or complete, bring it to a counselling appointment and ask.Commonly believed
Four things families assume after a failed test
"The test failed because something is wrong with my genes."
A failure is almost always about the sample, its transport or its paperwork. Faulty genes do not stop a laboratory from reading DNA. The DNA of a carrier reads just as easily as anyone else's.
"No news means it came back normal."
A failed test is not a normal result. If you were never told an outcome, ask. Families sometimes assume silence means good news when the sample was quietly rejected weeks earlier.
"An inconclusive result is probably positive."
It is not a leaning either way. It means part of the answer is missing. Treating it as a positive result can lead to worry, extra scans and even surgery nobody needed.
"If it failed once, it will fail again, so why bother."
Most repeats succeed once the cause is known and fixed. A different sample type, better transport or a second testing method usually gets the answer the first attempt could not.
Questions we are asked
Common questions about failed and unclear genetic tests
Do I have to pay again for a repeat test?
It depends on the laboratory and on why the test failed. When the failure was on the laboratory's side, many repeat it without charge. When the sample was clotted, late or mislabelled before it arrived, a charge is more likely. Ask for the policy in writing before the new sample is taken.
How long does a repeat usually take?
Roughly as long as the first test, sometimes a little less because the paperwork is already in place. A different sample type, such as a skin sample, can add time because the cells may need to be grown first. Your counsellor can give you the laboratory's own estimate.
Can the same sample simply be tested again?
Sometimes. If the laboratory still holds enough DNA and the problem was a single step in the process, it may rerun it. If the DNA itself was too little or too damaged, a fresh sample is the only way forward.
My relative's tissue block failed. Is that the end?
Not always. Another block from the same surgery may hold better DNA, so ask the hospital that stored it. If none works, a counsellor may suggest testing a living relative first instead, and explain carefully what that result can and cannot tell you.
Why would they want a skin sample instead of blood?
When blood does not reliably carry only your own inherited DNA. After a donor transplant it carries the donor's. During an active blood cancer it can carry changes from the cancer cells. A small skin sample gives a cleaner reading of what you were born with.
Should an inconclusive result change my treatment?
Not on its own. Treatment and screening decisions should rest on clear results and on your family history. If someone suggests a change based on an unclear report, it is reasonable to ask for a genetic counsellor to review it first.
Is a failed test the same as a variant of uncertain significance?
No. A failed test produced no reading. A variant of uncertain significance is a clear reading of a spelling difference whose meaning is not yet known. The first needs a repeat. The second needs time, and a way for you to be told if it is ever reclassified.
How do I avoid a failed sample the second time?
Follow the kit instructions exactly, especially for saliva. Check that your name and date of birth match your identity documents. Ask when the courier collects, so blood is not left waiting over a weekend, and mention any transplant or transfusion on the form.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
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Sources
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
- MedlinePlus Genetics — What do the results of genetic tests mean?
- MedlinePlus Genetics — How is genetic testing done?
- NHS — Predictive genetic tests for cancer risk genes
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
How to read a germline genetic test reportWhere each section of the report sits and what it saysVariant of uncertain significance in a germline reportThe unclear result that is often mistaken for a failed testWhen the report says no reportable variantsWhat a completed test with nothing found actually meansLow-level mosaic findings on a germline reportWhy a faint signal can leave a result unsettled
Talk to us
Told your test failed and not sure what happens now?
Share what the laboratory or your doctor told you, and we will explain the usual next step and whether a repeat or a different sample makes sense. One helpline serves every CION centre.