What is FISH testing on spermatozoa?
FISH (Fluorescence In Situ Hybridization) on spermatozoa is a technique used to study the genetic material of male gametes.
Humans are Diploids, which means we have two copies of each of the 23 types of chromosomes. Gametogenesis gives rise to cells (eggs or spermatozoa) that are Haploids, meaning they contain only a single copy of each of the chromosomes.
Gametogenesis is not an 100% efficient process and there is a certain proportion of gametes with an abnormal number of chromosomes (aneuploidy). The problem arises when aneuploidy levels are high.
A FISH analysis of the ejaculate will allow us to determine the levels of spermatozoa with abnormal chromosomal endowment and tell us whether or not they exceed the normal limits.
The chromosomes of the spermatozoa are studied by way of specific fluorescent probes for each chromosome. These probes are fluorescently labelled DNA fragments (each chromosome is assigned a different colour), so that when observed under a fluorescence microscope they can be distinguished from each other. These signals facilitate the study of how many copies of each chromosome there are in each spermatozoa.
Sexual abstinence is not required in order to undertake this test.
The FISH test on spermatozoa generally analyses 5 chromosomes, the sex chromosomes (X and Y) and chromosomes 13, 18 and 21. This study can be extended to other chromosomes if the clinical history indicates this would be advisable.
When is a FISH test on spermatozoa recommended?
The FISH test on spermatozoa is recommended in the following cases:
- Couples with repeat miscarriages.
- Implantation failures.
- Males with low seminal quality.
- Males with altered karyotypes.
- Patients with failed IVF (In Vitro Fertilisation)
What happens if FISH levels are abnormal?
The FISH is considered abnormal when the percentage of spermatozoa with altered chromosomal endowment exceeds the limit of the reference value.
A patient with a pathological FISH on spermatozoa is a patient with a higher risk of generating embryos with chromosomal alterations, and therefore, these embryos will have a lower implantation capacity, higher risk of miscarriages and a higher possibility of live newborns with altered karyotypes.
The alternative in these cases is to undertake a Preimplantational Genetic Diagnosis. This technique allows us to study certain genetic diseases that affect embryos before making the transfer.
In order to perform the Preimplantational Genetic Diagnosis, we need to undertake an In Vitro Fertilisation (IVF) cycle, from which we obtain embryos. From these embryos we will then extract a blastomere (cell) and analyse the genetic endowment of each embryo for a given alteration. This enables us to obtain more complete information about each of the embryos and allows us to choose the healthy ones to transfer.
Another alternative is the use of banked semen, in case of low seminal quality, and if the anomalies detected in the FISH test affect most of the chromosomes analysed.
FISH test on spermatozoa in Madrid
At Fertility Madrid, we have the latest technology used to perform the most advanced assisted reproduction techniques.You can undergo the FISH test on spermatozoa at our assisted reproduction clinic. Book an appointment or contact us for more information.