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What is DNA FRAGMENTATION INDEX (DFI)

04/03/22

Sperm DNA fragmentation is a new test for assessing male infertility. With the DFI test, the percentage of DNA fragmentation (DNA Fragmentation Index) of sperm can be calculated.

The genetic integrity of the sperm plays an important role in the normal development of the fetus. DNA is in the form of a double helix which is stabilized by chemical bonds. Breaking these bonds makes the helix unstable and the sperm may become more sensitive to the effects of harmful agents. This instability in sperm DNA is called fragmentation. The alteration in the structure of sperm DNA (sperm DNA fragmentation) is not reflected in any of the conventional parameters of the sperm diagram (motility, concentration, morphology).

DNA fragmentation has been the subject of many studies and has been associated with poor embryonic development, reduced implantation and pregnancy rates, and miscarriages, especially when fragmentation rates exceed 30%.

Extensive research in recent years has shown that regardless of the assisted reproduction method followed by a couple to have a child, the high percentage of fragmented DNA in the husband’s sperm significantly reduces the chance of a successful pregnancy.

It usually occurs in sperm that show low motility and poor morphology. However, high percentages have also been observed in sperm samples that show normal parameters, a fact that links the fragmentation of sperm DNA with cases of unexplained infertility.

Causes of DNA fragmentation in sperm

DNA fragmentation is usually caused endogenously by oxidative stress and abnormalities in the process of sperm apoptosis. Apoptosis is a normal biological process for the removal of “aged” sperm in the sperm of all men. Causes of fragmentation can be various exogenous factors, such as exposure to environmental and toxic substances, smoking, age of the man, exposure to high temperatures, chemotherapy, etc., as well as endogenous factors during spermatogenesis.

Which patients can benefit from the examination?

The DFI test is recommended for men:

• With abnormal sperm count

• For couples with recurrent miscarriages

Cases of couples with Low quality embryos or non-blastocyst formation after previous IVF attempts

• With Varicose Veins

Reference prices

After proper processing in the laboratory, the DNA of the sperm is denatured and their nuclear proteins are removed (Halosperm Kit), which leads to the creation of halo. Thus, they acquire a different morphology from those that carry intact DNA. According to the international literature, the results are divided into three important categories according to the DNA Fragmentation Index -% DFI (percentage of sperm with fragmented DNA). The following categories are distinguished:

• <15% DFI high potential fertility

•> 15% to <30% DFI good potential fertility

•> 30% DFI low potential fertility

The result is defined as normal when the fragmentation index (%) in the semen is below 30%.

Normal pregnancies occur even in couples where the husband has a high rate of DNA fragmentation in the sperm but with a reduced chance and increased risk of miscarriage.

Advantages of examining the percentage of fragmented DNA in the sperm

Genetic testing of DNA fragmentation in sperm is a reliable method of analyzing the integrity of sperm DNA, which can help detect men with poor prognosis in terms of ability to achieve pregnancy. It can also help diagnose, treat and treatment of unexplained male infertility as well as be an important prognostic value in evaluating the effects of assisted reproduction.

  1. The Practice Committee of the American Society for Reproductive Medicine. 2006. The clinical utility of sperm DNA integrity testing. Fertility and Sterility. 86: S35 – S37.
  2. Sakkas D., Alvarez J. G. 2010. Sperm DNA fragmentation: mechanisms of origin, impact on reproductive outcome, and analysis. Fertility and Sterility. 93: 1027 – 1036.
  3. Saleh R.A., Agarwal A., Nelson D. R., Nada E. A., El-Tonsy M. H., Alvarez J. G., Thomas A. J. Jr, Sharma R. K. 2002. Increased sperm nuclear DNA damage in normozoospermic fertile men: a prospective study. Fertility and Sterility. 78: 313 – 318.

Kyparissia Kostoglou,

 BcS, Junior Clinical Embryologist