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Ask The Nurse: Chromosome testing and FiSH

In this month’s blog, we answer some of the questions we get asked about chromosome tests

Ask The Nurse // 5th November 2021

Patients undergo several tests and investigations as part of their diagnosis and ongoing treatment for myeloma. This can include blood tests, bone marrow biopsies and scans. One of the tests myeloma patients, carers, and family members often ask us about are FiSH (Fluorescence in-situ hybridisation) or chromosome tests. These queries can come from people wanting to know more about these tests or people looking for information or reassurance after receiving their results.

This month’s blog answers some of your questions on how chromosome tests work, what the results can mean and whether you should receive chromosome tests.

What are chromosome tests?

Chromosome tests look for changes in a cell’s genetic material; its DNA (deoxyribonucleic acid).

DNA is a molecule found in cells that acts as a code containing all the instructions your body needs to live and grow. It tells a cell what to do and is responsible for determining how your body develops, for example, what colour hair and eyes you have.

The DNA in your cells is packaged into structures called chromosomes. Nearly every healthy cell within the body (except for the egg, sperm, and red blood cells) has 23 pairs of chromosomes.

Ask the nurse chromosomes

Chromosome tests, sometimes called cytogenetic tests, look at the number and structure of the chromosomes in myeloma cells to see if there are any changes compared to normal healthy cells.

Identifying chromosomal changes can help healthcare teams know more about a person’s myeloma. For example, they can find out if there are any chromosomal changes that could mean their myeloma is more challenging to treat, known as ‘high-risk’ changes.

How are samples for chromosome tests collected?

Two types of tissue samples are collected:

  • A blood sample; to collect DNA from a normal cell (not a myeloma cell)
  • A bone marrow sample; to collect DNA from a myeloma cell

The samples are sent to a laboratory; DNA is extracted from the samples and used for testing.

What chromosome tests are used in myeloma?

Two different tests are used in myeloma to detect chromosomal changes in cells.

Fluorescence in-situ hybridisation (FiSH): a test which uses fluorescent dyes and ultraviolet light to detect the presence of specific chromosomal changes.

In myeloma, FiSH tests are used to look for changes to the structure of chromosomes.

The three types of structural changes to chromosomes are:

  • Chromosome deletion: when a part of a chromosome is missing
  • Chromosome gain (duplication/addition): when a part of the chromosome is duplicated, and the same section appears more than once
  • Chromosome translocation (rearrangement) – is when a chromosome structure has been mixed up, and sections switched around

 

ask the nurse chromosomes

Karyotyping: a test examining the number and appearance of chromosomes. This test can determine if any chromosomes are missing, repeated, or damaged.

In myeloma, karyotyping is used to view changes in the number of chromosomes. When a cell has too few chromosomes, it is known as hypodiploidy, and if there are too many it is known as hyperdiploidy. Your healthcare team may also use the terms ‘trisomy’ and ‘monosomy’ – trisomy means three chromosomes (one extra), and monosomy is one (one less).

What do the results of chromosome tests mean?

In myeloma, chromosome tests give healthcare teams more information about a patient’s myeloma and can provide them with an indication of how aggressive or difficult to treat it could be.

You may be given a risk status – standard, high, or very high-risk based on the results. Patients with high or very high-risk myeloma can find that they do not respond as well to treatment and are more likely to relapse quickly.

The chromosomal changes associated with standard-risk myeloma are:

  • Hyperdiploidy
  • t(6;14)
  • t(11;14)

The chromosomal abnormalities associated with high-risk myeloma are:

  • 1q gain
  • del 1p
  • del 17p
  • t(14;20)
  • t(14;16)
  • t(4;14)

Very high-risk patients typically have at least one high-risk chromosomal change.

Although it can be worrying to find out that you have high- or very high-risk cytogenetic changes, it does not necessarily mean you have a worse prognosis. It just means there is a higher risk of it being more challenging to treat. Your doctor may suggest a slightly different treatment approach and offer a more intensive treatment, such as tandem high-dose therapy and stem cell transplants.

If you are worried or concerned about your tests results, speak to your doctor or nurse, who will be able to explain what it means for you and your treatment.

I have not had chromosomal tests. Should I ask for them?

It is recommended that all patients receive chromosome tests at diagnosis to determine any high-risk changes in their myeloma cells. Some patients will be retested at relapse.

Not all patients receive chromosomal tests as access will depend on the capacity and protocol in their area.

Patients might have access to testing through a clinical trial where samples are used in research with their consent.

If you would like chromosomal testing for free from the NHS, speak to your healthcare team to see what is available to you.

For more information about tests and investigations, you can read the Myeloma UK “Tests and investigations in myeloma Infoguide” or watch our video on genetics.

If you have any questions about imaging tests, you can contact us on the Infoline (0800 980 3332 (UK) or the Ask The Nurse email service.