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Medical glossary

PCR: polymerase chain reaction

PCR is a laboratory method that copies a particular piece of DNA or RNA millions of times so that it can be detected. It is very sensitive.

Last updated: ~1 min read
A PCR machine (thermal cycler) in a genetics laboratory with a DNA helix on its screen
Figure 1.A PCR machine copies DNA millions of times

01Short answer

In leukaemia, PCR is used to find specific genetic changes (for example BCR::ABL1, PML::RARA or NPM1) and measure how much is present. Quantitative PCR (qPCR) allows treatment response and MRD to be tracked: the trend in the number matters. The result is usually given as a percentage or ratio, and it is best compared within the same laboratory.

02Simple explanation

Copies DNA.

Very sensitive.

Measures amount.

For monitoring.

03Scientific explanation

NCI: PCR is a laboratory method that makes many copies of a specific piece of DNA.

The NCI Dictionary explains cancer terms in plain language; check the exact meaning for your situation with your doctor.

04What happens in the body?

What it is for

Diagnosis, risk group and MRD monitoring.

The machine
Figure 2.The machine — PCR: polymerase chain reaction

Reading the result

Look at the trend and discuss it with your doctor.

Multiplying
Figure 3.Multiplying — PCR: polymerase chain reaction

Where you will see this word

In test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.

Ask your doctor

The general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

05From an unfamiliar word to a clear answer: four steps

Write it down, look it up, prepare a question, ask.

Write it down — From a result or a conversation.1Write it downFrom a result or a conversation.
Look it up — Learn the plain meaning.2Look it upLearn the plain meaning.
Prepare a question — What does this mean for me?3Prepare a questionWhat does this mean for me?
Ask — Your doctor gives the personal explanation.4AskYour doctor gives the personal explanation.
UnderstandingResults feel less frightening.
ConversationA shared language with your doctor.
SafetyNot drawing conclusions alone.

06Key points at a glance

TopicIn brief
What it is forDiagnosis, risk group and MRD monitoring.
Reading the resultLook at the trend and discuss it with your doctor.
Where you will see this wordIn test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.
Ask your doctorThe general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

07Key terms

qPCR
Quantitative PCR.
Fusion gene
Two genes joined together.
Term
A word with a precise medical meaning.
Reference range
The range a laboratory considers normal.

08Key points

  • Learn.
  • Ask your doctor.
  • Write it down.
  • Write the word down.
  • Ask what it means.

09Frequently asked questions

My PCR result went up: should I worry?

Small changes happen; your doctor will explain what it means.

What sample is needed?

Blood or bone marrow.

This word is in my results: should I worry?

The word itself does not mean a serious or mild condition; get the explanation from your doctor.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. My PCR result went up: should I worry?

  2. What sample is needed?

  3. This word is in my results: should I worry?

My questions

12Sources

  1. National Cancer Institute. NCI Dictionary of Cancer Terms: polymerase chain reaction
  2. National Cancer Institute. NCI Dictionary of Cancer Terms: minimal residual disease
  3. National Cancer Institute. NCI Dictionary of Cancer Terms
  4. National Cancer Institute. Leukemia
  5. American Cancer Society. Neutropenia (Low White Blood Cell Counts)
  6. National Cancer Institute. NCI Dictionary of Cancer Terms: bone marrow aspiration
  7. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: white blood cell
  8. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: neutrophil
  9. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: neutropenia
  10. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: bone marrow biopsy
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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