Understand a test before, during and after

A small sample of blood from a vein, tested for things like red and white blood cells, platelets, iron, and liver and kidney function.

Doctors may consider this test:

• To look for anaemia, infection or signs of a blood disorder
• To check how organs are working before or during treatment
• To help decide which further tests are needed

A quick needle in the arm, usually a few minutes. Some tests need fasting: ask when booking.

Preparation: Usually none. Some tests need fasting.

• What are you checking for with this test?
• When and how will I get the results?
• What would an abnormal result mean for next steps?

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• Many results are affected by infections, medicines and hydration
• Normal ranges differ slightly between laboratories

Proteins or other substances such as PSA (prostate), CA-125 (ovary), CEA (bowel) and AFP (liver) that some cancers produce in larger amounts.

Doctors may consider this test:

• To help monitor a known cancer during and after treatment
• As one piece of information when a specific cancer is suspected
• PSA may be discussed for prostate checks after talking through pros and cons

A standard blood test.

Preparation: For PSA, avoid ejaculation and vigorous cycling for about 48 hours before the test; ask your clinic.

• Why is this marker being checked for me?
• What else can raise this marker?
• Will one result be enough, or do we need to watch the trend?

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• Raised levels are common in non-cancer conditions such as infection, inflammation, benign prostate enlargement or endometriosis
• A normal level does not rule cancer out

A handheld probe with gel on the skin sends harmless sound waves and turns the echoes into an image. No radiation is used.

Doctors may consider this test:

• To see whether a lump is a fluid-filled cyst or solid
• To look at organs such as liver, kidneys, ovaries and thyroid
• To guide a needle during a biopsy

Painless, usually 10 to 30 minutes. Some pelvic scans need a full bladder, and some are done with an internal probe.

Preparation: Depends on the area: you may be asked to fast or drink water beforehand.

• What exactly are you looking at?
• Will the person scanning be able to tell me anything today?
• If something is found, what happens next?

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• Quality depends on the operator and the body area
• Some findings need a different scan or a biopsy

You lie on a table that moves through a ring-shaped scanner. A contrast dye may be given by injection or drink to make structures clearer.

Doctors may consider this test:

• To look for the cause of symptoms in the chest, abdomen or pelvis
• To see whether cancer has spread (staging)
• To check response to treatment

The scan itself takes a few minutes. Contrast can cause a brief warm feeling. Tell staff about kidney problems or allergies.

Preparation: You may need to fast for a few hours if contrast is used.

• Why is CT the right scan for this question?
• Will I need contrast, and is it safe with my kidneys and allergies?
• What does the radiation dose mean for me?

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• Uses ionising radiation, so scans are used when the benefit outweighs the small risk
• Can find incidental findings that need follow-up but turn out to be harmless

You lie inside a tunnel-shaped scanner. No ionising radiation is used. A contrast injection may be given.

Doctors may consider this test:

• To look closely at the brain, spine, prostate, pelvis, liver or breast
• To plan surgery or radiotherapy
• To check a finding seen on another scan

Usually 20 to 60 minutes and noisy (earplugs or headphones are offered). Tell staff about metal implants, pacemakers or feeling claustrophobic.

Preparation: Remove metal items. Some scans need fasting.

• Is MRI safe with my implants or devices?
• Can I have something to help if I feel claustrophobic?
• How long will the scan take?

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• Longer and more expensive than CT
• Movement can blur images

A tracer (often a type of sugar called FDG) is injected. Cells that use more energy, including many cancer cells, take up more tracer and show up on the scan.

Doctors may consider this test:

• To stage some cancers and see whether they have spread
• To check response to treatment in some cancers such as lymphoma
• To investigate specific questions after other scans

You rest quietly for about an hour after the injection, then the scan takes 20 to 45 minutes. Drink plenty afterwards.

Preparation: Usually fasting for several hours; special instructions for people with diabetes.

• What question will this PET scan answer?
• Do I need to fast or adjust diabetes medicines?
• Should I avoid close contact with babies or pregnant people afterwards?

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• Inflammation and infection can light up too
• Some slow-growing cancers do not show up well

Each breast is gently pressed between two plates for a few seconds while X-ray images are taken, usually two views per breast.

Doctors may consider this test:

• Screening people without symptoms at ages set by local programmes
• Checking a lump or other breast change (a diagnostic mammogram)

The pressing can be uncomfortable for a few seconds. The appointment usually takes about 15 to 30 minutes.

Preparation: Avoid deodorant or talc on the day if possible; wear a two-piece outfit.

• Is this a screening or a diagnostic mammogram?
• Do I have dense breasts, and what does that mean for me?
• What happens if I am called back?

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• False positives lead to recalls; most recalls do not find cancer
• Can find slow-growing cancers that would never have caused harm (overdiagnosis)

A small soft brush collects cells from the cervix during a short examination with a speculum.

Doctors may consider this test:

• Cervical screening in some programmes
• As a follow-up test after a positive HPV result

Usually takes a few minutes and can feel uncomfortable. You can ask for a smaller speculum, a female clinician or a chaperone.

Preparation: Book outside your period if you can; avoid vaginal creams for two days before.

• Is my test HPV-based, cytology-based or both?
• When will I get results, and what do the categories mean?
• Is self-sampling an option for me?

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• Less sensitive than HPV testing; many programmes now test for HPV first
• Results are sometimes unclear and need repeating

A sample from the cervix or vagina is tested for high-risk HPV. In many places a self-collected vaginal swab is an option.

Doctors may consider this test:

• As the main cervical screening test in many countries
• To decide who needs further checks

Either a clinician sample like a smear test, or a simple swab you take yourself.

Preparation: Usually none.

• Can I take my own sample?
• If HPV is found, what are the next steps?
• Does the HPV vaccine change my screening?

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• Most HPV infections clear on their own, so a positive result is common and usually not serious
• Screening intervals and ages differ between countries

A tube with a camera passes through the back passage along the bowel. Samples can be taken and small growths (polyps) removed.

Doctors may consider this test:

• To investigate symptoms such as bleeding or a change in bowel habit
• Follow-up after a positive stool test (FIT)
• Screening in some countries

The bowel is emptied with a strong laxative the day before. Sedation or pain relief is usually offered. The test takes 30 to 45 minutes.

Preparation: Diet changes and bowel preparation for one to two days. Ask about blood thinners and diabetes medicines.

• Will I have sedation, and do I need someone to take me home?
• What happens to any polyps you remove?
• When will I know the biopsy results?

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• A small risk of bleeding or a tear in the bowel
• The preparation is unpleasant for many people

A sample is removed with a needle, during an endoscopy, or in a small operation. It is sent to a laboratory for examination.

Doctors may consider this test:

• To confirm whether an abnormal area is cancer
• To find the exact type and features of a cancer, which guide treatment

Most needle biopsies use local anaesthetic and feel like pressure. You may have some bruising or soreness for a few days.

Preparation: Depends on the site; you may need to stop blood thinners after checking with your team.

• What type of biopsy will I have, and will it hurt?
• When and how will I get the results, and who will explain them?
• Should I stop any medicines such as blood thinners beforehand?

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• A small risk of bleeding or infection
• Results can be inconclusive and need repeating

A report describing whether cells are cancerous, the type of cancer, its grade, and other features such as receptors or margins after surgery.

Doctors may consider this test:

• To give a diagnosis
• To guide treatment choices together with scans and other tests

You do not attend this test. Your team receives the report and discusses it with you.

Preparation: None.

• Can you explain my report in plain language?
• Can I have a copy?
• Was a second specialist opinion done, or can I ask for one?

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• Reports use technical language, so ask for an explanation
• Some features need extra tests that take longer

Germline tests look for inherited gene changes that raise risk in a family, such as BRCA1 or BRCA2. Tumour tests look for changes inside cancer cells that can guide treatment.

Doctors may consider this test:

• To check inherited risk when family history suggests it
• To find tumour changes that match a targeted treatment or a clinical trial

Germline: a blood or saliva sample, usually after genetic counselling. Tumour: uses tissue already taken at biopsy or surgery.

Preparation: Genetic counselling is recommended before germline testing.

• Is this an inherited test or a tumour test?
• What could the result mean for my relatives?
• How is my genetic data stored and who can see it?

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• Results can show variants of uncertain significance
• Consumer tests are not a substitute for clinical testing with counselling

Tumours can shed tiny amounts of their DNA, and sometimes whole cells, into the blood. A liquid biopsy looks for these signals in an ordinary blood sample. Different tests look for different signals, and each has its own uses and limits.

What a liquid biopsy can look for

• Circulating tumour DNA (ctDNA)Fragments of tumour DNA mixed in with the normal cell-free DNA (cfDNA) in plasma. Used to look for treatment-guiding gene changes and, in trials, leftover disease after treatment.
• Circulating tumour cells (CTCs)Whole cancer cells that have broken away from a tumour into the blood. They are very rare, often a few among billions of blood cells. Counting them can help estimate outlook in some advanced cancers, and they can be studied for markers.
• DNA methylation and fragment patternsChemical tags and fragment sizes on cell-free DNA that differ between cancer and healthy cells. Many multi-cancer early detection tests use these.
• Other signalsTumour proteins, RNA and tiny vesicles called exosomes. These are mostly still being researched.

Doctors may consider this test:

• To find treatment-guiding gene changes (ctDNA) in some advanced cancers when tissue is hard to get (an established use)
• To count circulating tumour cells (CTCs) as a guide to outlook in some advanced breast, prostate and bowel cancers (a specialist use)
• To look for leftover disease after treatment (emerging, mostly in trials)
• Multi-cancer early detection in people without symptoms (investigational)

A standard blood draw, sometimes into special tubes that keep DNA or cells stable until they reach the lab.

Preparation: Usually none.

• Which job is this test being used for: treatment matching, monitoring or screening?
• What happens if the result is positive, and who will arrange follow-up?
• Is this test part of standard care or a trial where I live?

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• Early-stage cancers may shed too little DNA, or too few cells, to detect
• CTCs are extremely rare, so counts can vary between samples, and a count alone does not guide most treatment decisions
• Ageing blood cells can carry mutations that mimic tumour DNA
• No multi-cancer early detection test has yet been shown to reduce cancer deaths