SDI® test

In order to examine the sperm DNA, a special test must be carried out as the standard examination of sperm quality does not provide any information about how well the DNA is protected.

The SDI® test determines whether the sperm DNA is robust or fragile.
SDI is an abbreviation of Sperm DNA Integrity.
Good integrity means that the sperm DNA is robust.

The SDI® test

The team at SPZ Lab have been working with sperm DNA testing since 2000.

The SDI® test is an advanced version of the Sperm Chromatin Structure Assay (SCSA®), which was originally developed by the American researcher, Donald P. Evenson.

Quality control is more comprehensive in the SDI® test, which means the level of precision is approximately 50% higher than it is in the SCSA®. The test is based on the use of flow cytometry, which makes it possible to analyze thousands of sperm cells per measurement.

DFI varies from 0 to 100%. A low DFI indicate that the DNA is robust. The higher the DFI is, the more fragile the DNA is.


The result of the SDI® test is a DFI value.

Originally, DFI was an abbreviation of ‘DNA Fragmentation Index’ as the test examines whether the DNA is fragile. But we think the name is a bit misleading, which is why today we say that DFI stands for ‘DNA Fragility Index’.

The DFI can vary from 0 to 100. The ideal is to have a very low DFI as this means that the sperm DNA is very robust.

The higher the DFI value, the more fragile the sperm’s DNA.

The levels of DFI, their consequences for couples, and the proportion of couples affected are presented below.

DFI under 15

  • The DFI is normal, and the sperm DNA is robust.
  • Approximately 50 % of examined couples are in this group.

DFI between 15 and 25

  • The DFI is increased, and the likelihood of pregnancy is approximately halved.
  • This group accounts for approximately 25 % of examined couples.
  • The increased DFI means that achieving a pregnancy takes longer. At the same time, pregnancies end in miscarriages more frequently. These problems increase as the DFI increases.

DFI over 25

  • The DFI is high, and the likelihood of pregnancy is only about 10% of what is considered normal.
  • This group represents about 20% of examined couples.
  • The majority of couples are unable to achieve pregnancy and the risk of miscarriage is very high.