Blood tests for CLL

Blood tests are the most important tests for chronic lymphocytic leukaemia (CLL). You have a number of different blood tests to help with your diagnosis.

Blood tests can:

  • check your general health, including how well your liver and kidneys are working
  • check numbers of blood cells
  • help diagnose cancer and other conditions

Your blood is sent to the laboratory where it is studied under a microscope to count the different types of cells. This is called a full blood cell count (FBC). The blood will also be checked to see whether the cells look normal or not.

Preparing for your blood tests

You can eat and drink normally before most blood tests. For fasting blood tests you need to stop eating and drinking beforehand. Your doctor will tell you for how long.

What happens?

You sit or lie down to have the test.

A doctor, nurse or phlebotomist (person specialised in taking blood) chooses the best vein to use. This is usually from your arm or hand. Let them know if you are afraid of needles, get unwell with the sight of blood or are allergic to plasters or latex. 

They put a tight band (tourniquet) around your arm above the area where they take the sample. You may need to clench your fist to make it easier to find a vein.

They clean your skin and then put a small needle into your vein. Next, they attach a small bottle or syringe to the needle to draw out some blood. They might fill several small bottles.

Once they have all the samples, they release the band around your arm. They then take the needle out and put pressure on the area with a cotton wool ball or small piece of gauze for a few minutes. This helps to stop bleeding and bruising.

Look away when they’re taking the blood if you prefer. Tell your doctor, nurse or phlebotomist if you feel unwell.

Getting your results

Ask the phlebotomist, doctor or nurse when and how you will get your results. Some results might be available very quickly, such as a full blood count and kidney and liver function tests. Other tests might take several weeks.

Possible risks

Blood sampling (phlebotomy) is a safe test. There is a possibility of:

  • bleeding and bruising - pressing hard when the needle is removed can help to stop it
  • pain - this is normally mild and can last for a few minutes
  • swelling (oedema) - ask your nurse, doctor or phlebotomist to avoid an arm that is swollen or has a risk of swelling
  • feeling faint or fainting - tell the person doing your blood test if you're feeling lightheaded or dizzy at any time
  • infection - this is very rare

Types of blood tests

Full blood count

A full blood count (FBC) measures the number of red cells, white cells and platelets in your blood.

  • Red cells carry oxygen around our bodies. Haemoglobin is the part of the cell that carries oxygen. If you have a low red cell count, your doctor might say you’re anaemic (pronounced a-nee-mic). This can make you feel tired, short of breath and dizzy.
  • White cells fight infections. There are several different types of white cells, including neutrophils and lymphocytes.
  • Platelets help clot the blood, for example after a cut. Symptoms of a low platelet count include abnormal bleeding, such as bleeding gums and nosebleeds.

There is a range of normal for blood counts. The range of figures quoted as normal varies slightly between laboratories and also differs between men and women. 

Diagram of table showing the normal values of men and women

Testing for proteins on the surface of leukaemia cells (immunophenotyping)

Doctors look for certain proteins (antigens) in your blood sample. These antigens are on the surface of leukaemia cells. This test is called immunophenotyping.

A specialist diagnostic laboratory does the test. Doctors use a technique called flow cytometry to do immunophenotyping. This process uses antibodies to find cells with certain antigens on their surface. Doctors do this test on a blood, bone marrow or fluid sample. 

This is the most important test when a doctor thinks you might have CLL. The results are usually all your doctor needs to confirm a diagnosis of CLL.

Testing for gene changes

Your haematologist will order a test to look for changes (abnormalities) in your genes. Your doctors can do these tests on your blood and bone marrow samples.

The doctors are looking for changes in genes and chromosomes in the leukaemia cells. This is different to testing you to see if you have an inherited faulty gene that increases your risk of getting cancer.

FISH (fluorescence in situ hybridisation) is a test that looks for gene changes in cells. These tests are also called cytogenetic tests or molecular analysis.

Doctors are looking for changes in specific genes, for example the:

  • TP53 gene
  • IGHV gene

These genetic tests help your doctor understand more about your outlook and make decisions about your treatment.

Urea and electrolytes

These blood tests show how well your kidneys are working. Waste chemicals called urea and creatinine are produced by the body. Our kidneys remove them from our blood and get rid of them in our urine.

Electrolytes are substances such as sodium, potassium, chloride and bicarbonate.

Liver function tests (LFTs)

Liver function tests (LFTs) check how well your liver is working. LFTs look for levels of enzymes and proteins made by the liver or which are cleared by the liver. They include:

  • alanine aminotransferase (ALT)
  • aspartate aminotransferase (AST)
  • alkaline phosphatase (ALP)
  • gamma-glutamyl transferase (Gamma GT)

They might be raised if you have a blockage in your liver or bile duct, or if you drink a lot of alcohol.

LFTs also look at the amount of bilirubin in the blood. This is a chemical in bile Open a glossary item. Bilirubin can be raised if you have a problem with your liver or gallbladder. Bilirubin can cause yellowing of your skin and eyes (jaundice). 

LFTs also measure albumin. This is a protein in the blood that can be low when you have some types of cancer. You can also have low albumin if you’ve been eating small amounts and are malnourished.

Other blood tests

You might have other tests to check for:

  • a blood protein called beta 2 microglobulin (B2M)
  • certain antibodies - this test is called a direct anti-globulin test (DAT)
  • serum immunoglobulins (Igs)
  • lactate dehydrogenase (LDH)

All these tests will help with your diagnosis and to plan your treatment.

Last reviewed: 
18 Sep 2021
Next review due: 
18 Sep 2024
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