General Information

What Sort of Tests are Available?

1. Paternity Tests

The most evident and common application of a paternity test is to determine whether an alleged father is in fact the biological father of a child. This information could be helpful for a number of reasons:

Two main types of paternity tests are generally offered:

As long as the correct procedure is followed for sample collection there should be no difference in the accuracy and validity of the results obtained by either of these two.

The main difference between the two tests lies in the admissibility of the results as evidence in the Courts of Law. The requirements for a Legal paternity test to be officially recognised in Court vary between countries, but in general there must be an independent third person, usually a lawyer or a court-appointed expert, who can testify that each of the samples tested in the laboratory really originated from the corresponding donor, and who can provide evidence that at no point could the samples have been switched or contaminated. The necessary involvement of a third person and the additional procedural steps that need to be employed, both by the legal representative and by the laboratory, naturally make the Legal paternity test more expensive. It is also usually necessary for the individuals choosing the Legal test to travel to the office or facility of the legal representative for the test to be performed.

Sample collection for the Curiosity paternity test can generally be carried out at home by the donors themselves. The procedure is easy to understand and can be performed by practically anybody.

In a few words, the choice between a Curiosity and a Legal paternity test depends on the intention of using the results as evidence in a legal dispute. If chances of this are low, then the Curiosity test offers equally valid results with more convenience and at a lower price.

Difference	Curiosity Test	Legal Test
Admissible in Court	No	Yes
At Home Test Possible	Yes	No
Identification Necessary	No	Yes
Consent Necessary	Consent necessary from all persons tested, and one of the legal parents if the child is a minor	Consent necessary from all persons tested, and both legal parents of the child
Price of the Test	340 € (incl. 50 € for kit)	640 € (incl. consultation)
Reliability	Very high	Very high
Turnover time	3 Weeks	3 Weeks

2. Maternity Test

Maternity tests are similarly employed to determine the relationship between a woman and a particular child. The test may be useful in cases of an abducted or abandoned child.

Other applications of paternity and maternity tests include:

3. Twin Test

A Twin Test determines if twins are identical or not. Identical twins share all of their genes and therefore have identical genetic profiles. Non-identical twins share a quarter of their genes on average, just like a brother and sister, and therefore their genetic profiles do not match perfectly. Genetic profiles do not change with time, so the tests may be applied to identify identical twins at any time throughout their lives.

Twin tests might be performed for several reasons:

4. Relationship Test

• Confirmation of relationships between reunited family members in case of adoption
• Determination of parentage or grand-parentage for insurance or inheritance rights claims
• Proving kinship to a citizen in order to substantiate claims for immigration status qualification

Information on DNA and Identity Tests

1. DNA and Chromosomes

Hereditary material called DNA (deoxyribonucleic acid) is the genetic blueprint of life. It determines the specific characteristics of each individual. Except for identical twins, every person's DNA is unique. Consequently, a unique genetic profile can be created from a person's DNA. This DNA profile forms the basis of identity tests.

DNA is a long threadlike molecule found in almost all cells of the human body. An individual's genetic makeup is coded within the DNA in several functional units called genes. The entire DNA content of practically all cells is located in 46 chromosomes. These are complex molecular structures consisting of a long DNA strand.

The 46 chromosomes are grouped into 23 pairs, of which 22 pairs are homologous, meaning that the paired chromosomes are of the same size and appearance and store information related to the same inherited traits. The 23rd pair comprises the sex chromosomes (X or Y) that are important for sex determination (a man has 1 X and 1 Y chromosome, whereas a woman has 2 X chromosomes). Each set of 23 chromosomes is inherited from one biological parent. Thus, every individual has two genetic complements in their DNA, one complement inherited from the biological mother and the other from the biological father. This fact forms the foundation on which DNA paternity testing is based, since it allows the biological relationship between a child and an alleged father to be validated or excluded by a comparison of their DNA.

2. DNA Identity Tests

In the previous section it was established that by comparing the DNA of a child and an alleged father, it is possible to investigate their biological relationship. In practice, only certain regions in the DNA, called microsatellite markers or loci, need to be compared to establish biological paternity. Microsatellite markers are short fragments of DNA in which the same DNA sequence is repeated several times. Since an individual has two genetic complements of DNA, there are actually two copies of each marker present, one inherited from each of the biological parents.

Depending on the laboratory, generally between 6 and 16 microsatellite markers are analysed for determination of paternity. The microsatellite markers used are standard markers recommended by specialised organisations such as the European Network of Forensic Science (ENFSI), the Iberoamerican Working Group on DNA Analysis (GITAD), and Interpol. An important property of these markers is that the number of DNA sequence repetitions (or frequency) is highly variable within the general population but strongly conserved from parent to child. As a result, the frequency of one complement of each of the child's markers matches that of one complement of the biological mother, whereas the frequency of the other complement matches that of one complement of the biological father (see Example 1).

The set of frequencies of the analysed markers constitutes the genetic profile of a tested individual. A standard paternity test determines the genetic profiles of the mother, the child and the alleged father. By comparing the three profiles it is possible to identify the marker in each complementary pair that the child inherited from the biological mother. By elimination, the remaining half of the genetic profile was inherited from the biological father. By comparing this part of the child's genetic profile with the profile of the alleged father, the Paternity Test determines whether the alleged father is the biological father or not. A match between the two profiles indicates that the alleged father is the real biological father (Example 1). On the other hand, if the profile of the alleged father does not match that of the child, he is excluded from paternity (Example 2).

3. Accuracy of a Paternity Test

Since it is so specific, DNA paternity testing is a very powerful form of testing. In a test including samples from the mother, child and alleged father, the probability of paternity is 99.9% or greater when an alleged father's DNA profile matches that of the child for all the genetic markers. On the other hand, an alleged father is 100% excluded from paternity if there is a mismatch between the profiles of the child and alleged father for three or more genetic markers.

When only a child and alleged father are tested (i.e. a motherless test), the information provided by the mother's DNA profile is unavailable. Nonetheless, when there is a perfect match between the DNA profiles of the child and alleged father, the probability of paternity is generally in excess of 99.9%. A mismatch in the two DNA profiles for three or more genetic markers implies with 100% certainty that the alleged father is not the child's biological father.

The accuracy of the test increases with the number of genetic markers included in the DNA profile. Thus, the result of a test that uses a 16-marker profile is likely to be more conclusive than one using a 6- or 13-marker profile. It is therefore important to select a paternity test that uses an adequate number of markers, especially when only the child and alleged father are tested.

Since family members are more likely to have similar genetic profiles, when two alleged fathers are related the probability of paternity may be lower than in standard tests. In such cases it is always best to test both alleged fathers, since the one who is not the biological father can be excluded with certainty. If the two alleged fathers are identical twins it is not possible to identify the biological father, since identical twins have identical DNA profiles.

The reason that it is not possible to determine biological paternity with 100% certainty is that there is always a very small possibility that the profile of the alleged father matches that of the child purely by chance. The likelihood of this happening is generally well below 0.001% (or 1 in 100000) and it depends to a large extent on the ethnic origin of the individuals involved. The certainty of biological paternity generally increases with the number of genetic markers analysed.

4. Example 1



Case 1: The figure shows the result for one microsatellite marker from a paternity test that includes samples from the mother (top row), the child (middle row), and the alleged father (bottom row). In this example, the maternal marker that has been passed to the child is number 6. This means that the other marker present for the child (number 7) must have been inherited from the father. In this case the alleged father matches the child, since one of his markers is indeed number 7. This procedure is repeated for all microsatellite markers used in the test.

5. Example 2



Case 2: The figure shows the result for one microsatellite marker from a paternity test that includes samples from the mother (top row), the child (middle row), and the alleged father (bottom row). In this case the maternal markers are 29 and 30. This implies that the child has inherited 29 from the mother and the 31.2 complement must have been inherited from the biological father. Since the alleged father does not possess this marker it is unlikely that he is the biological father. In practice this mismatch between the child and alleged father's DNA must be present in at least three markers to exclude paternity with certainty.

6. The At Home Kit

Saliva samples (also called oral swabs, mouth swabs, or buccal swabs)
For the personal paternity test and the twin test it is possible to use the special AT HOME KIT from GENDIA. This kit uses saliva as the source of DNA.
The procedure to obtain a saliva sample is simple and painless, and therefore this kit is commonly used.
It is recommended NOT to eat or drink at least one hour before a saliva sample is taken. Use a separate envelope and swab for each person. Please complete the information (name, date of birth, and identification: father/mother/child) on the envelop before taking the samples.
Take care not to touch the broad end of the swab, and to use a new sterile oral swab for each donor. Take the swab out of the plastic without touching the broad end, and throw away the plastic.
A sample is taken by gently rubbing the broad side of the swab 10 times against both cheeks, under the tongue and behind the lips, each time for 3 seconds. The swab is then put into the correct envelop without closing the envelope. Do NOT use the plastic to put the swab in.
Finally, put the small envelops in a larger envelop and send this to the GENDIA laboratory in Antwerp.

A typical at-home kit

How is a Test Performed?

1. Sample Registration

In case of curiosity testing the samples are usually taken at home with the at home kit and sent to the GENDIA lab. In case of legal paternity tests, the samples are usually taken by a GENDIA physician.

As soon as the samples reach the GENDIA lab they are registered in the lab's database. Here, data such as the case number and the date of sample receipt are recorded.

The case number allows the unique identification of a sample while keeping the donor anonymous to the laboratory personnel. Once results are obtained, the person in charge matches the identification numbers back to the sample donors in order to issue the test report.

2. DNA Extraction

The saliva or blood samples received by the laboratory contain the genetic material that is analysed in the paternity test. The genetic material is called DNA (Deoxyribo Nucleic Acid) and it is found in the centre (or nucleus) of the cells in the sample.
Before the DNA can be analysed it must first be extracted and purified from the other components in the sample.

The first step of the DNA extraction process is to break up (or lyse) the cells so that the DNA inside is released. This is achieved by adding a special solution to degrade certain components of the cell, leaving the DNA floating freely. The DNA is then dissolved in a liquid and is ready for the next step of the paternity test.

3. DNA Markers

Only specific small sections of a person's DNA need to be analysed in order to perform an identity test. These sections are referred to as DNA markers. These DNA markers vary between different persons, and a combination of different DNA markers therefore constitutes a person’s unique genetic profile. The more DNA markers are used, the more unique the genetic profile becomes. Most labs analyse 6 to 16 markers. GENDIA analyses 16 markers.

4. DNA Analysis

Once the DNA markers have been amplified, they are placed into an instrument called an automatic DNA analyser, which separates the markers by size. The size information is measured by means of a laser, fed into a computer, and analysed with a special software program.

The detection result is displayed in graphic form on the computer, as show in Example 1 and Example 2. Each DNA marker appears as two peaks, one from the father, and one from the mother.

5. Statistical Analysis

Once results from all samples for all the DNA markers have been collected, they are inputted into a statistical software program for interpretation. If a given marker does not match between a child and alleged father, it is likely that the latter is not the real biological father. For each additional non-matching there is an increase in the probability that the alleged father is not the biological father. In fact, if three or more markers do not match, it is practically impossible that the alleged father is the real biological father.

On the other hand, a match in the frequencies between an alleged father and a child for a given marker may occur for two reasons. It may either be that the alleged father is the real biological father. However it could also be that the two donors happen to have identical markers purely by chance. The larger the number of matching markers between a child and an alleged father, the higher the likelihood that the latter is the biological father. If more than 10 markers show a match between child and alleged father it is practically certain that the latter is the biological father.

The probability of paternity is defined as a percentage. If an alleged father is not the biological father, the paternity test generates a probability of paternity of 0%. If the alleged father is the biological father, the test usually generates a probability of paternity on the order of 99.9% or more.

6. The Test Report

The final step in the laboratory procedure for a test is to issue a report and dispatch it to the person requesting the test.
The report includes the following components: