Sperm Aneuploidy Test. 5 chromosomes: 13, 18, 21, X and Y
1. What is the SAT?
The Sperm Aneuploidy Test (SAT) is a diagnostic test to study the genetic etiology of male infertility. In particular, this test evaluates the percentage of spermatozoa with chromosomal abnormalities in a sperm sample.
This analysis allows the estimation of the transmission risk of chromosomal abnormalities to the offspring. This test analyzes the chromosomes mostly implicated in spontaneous miscarriages and affected offspring with chromosomal abnormalities (chromosomes 13, 18, 21, X and Y).
It is advised for the following indications:
- Couples with recurrent miscarriage
- Couples failing to conceive after several IVF treatments
- Infertile men with impaired sperm parameters
Aims of SAT are:
At the clinical level, an increase in spermatozoa with chromosomal abnormalities has been associated with a decrease in pregnancy rates and higher miscarriage risk in infertile couples undergoing ICSI cycles (Rubio et al., 2001; Burrello et al., 2003; Petit et al., 2005; Nicopoullos et al., 2008; Rodrigo et al., 2011; Rodrigo et al., 2013).
At the embryo level, different effects have been observed according to the type of sperm chromosomal abnormality. An increase in the percentage of spermatozoa with sex chromosome disomies, results in an increase embryo aneuploides compatible with life (Patau syndrome, Edwards syndrome, Down syndrome, Klinefelter syndrome, Turner syndrome and trisomies XXX and XYY). An increase in diploid spermatozoa generates an increase in triploid embryos, which mostly miscarry before delivery (Rodrigo et al., 2010).
At the offspring level, several studies performed in parents of children with Down, Klinefelter, and Turner syndrome have shown increases in sperm chromosomal abnormalities associated with the chromosomopathies observed in the children (Eskenazi et al., 2002; Tanget al., 2004; Blanco et al., 1998).
For these reasons, the Sperm Aneuploidy Test can help in the reproductive genetic counseling of infertile men to assess the optimal assisted reproduction approach.
2. Indications. For whom and when?
This is a diagnostic test directed to the study of male infertility, indicated for patients with higher sperm aneuploidy risk, that is, men with impaired sperm parameters, mainly oligozoospermia, non-obstructive azoospermia, and severe teratozoospermia.
Other indications, not necessarily associated with impaired sperm parameters are recurrent miscarriage of unknown etiology; couples failing to conceive after several IVF treatments and; couples with a previous pregnancy with chromosomopathy.
3. Advantages. Strengths among other tests?
Compared to classic meiotic studies, this test offers the advantage of assessing the final product of meiosis, the spermatozoon that will directly fertilize the ovum. An average of 2,000 sperm per chromosome is analyzed by two independent observers to obtain clinically relevant results. The percentage of chromosomally abnormal sperm is compared to a control group of fertile normozoospermic donors to assess for statistical differences.
1. What is the significance of an abnormal FISH on sperm?
- An increase in the percentage of spermatozoa with sex chromosome disomies, results in an increase in embryo aneuploidies, mostly for sex chromosomes, which are compatible with life. In contrast, an increase in diploid spermatozoa generates an increase in triploid embryos, which mostly miscarry before delivery.
- An increase in spermatozoa with chromosomal abnormalities has been associated with a decrease in pregnancy rates and higher miscarriage risk in infertile couples undergoing ICSI cycles.
- In parents of children with Down, Klinefelter, and Turner syndrome, several studies have shown increases in sperm chromosomal abnormalities for sex chromosomes and for chromosome 21.
2. What other chromosomes can be tested?
If a chromosomal abnormality was detected in a previous pregnancy, a customized SAT can be requested and additional FISH probes can be included in the test to target the implicated chromosomes.
3. Is sexual abstinence required before collecting the sperm sample for the test?
A previous period of 2-3 days of sexual abstinence is recommended before colleting the sample.
4. Is there a minimal sperm concentration required to perform an SAT?
There is not a minimal concentration to request a sperm test, the only requirement is the presence of any sperm, even in a concentration below 1 million sperm/mL and also in samples from the epididymis or testes. Seldom there are not enough sperm to perform the test, and additional samples can be requested.
5. Is it possible to perform an SAT in carriers of structural abnormalities?
It is possible to test sperm from carriers of translocations using DNA probes implicated in the chromosome rearrangement.