Accreditation and reliability

Accreditation and reliability of a DNA test: how to choose a trustworthy laboratory?

When considering a DNA test (paternity, maternity, siblingship, indirect filiation, genealogy), one question always arises: will the results be reliable?

Reliability depends on several factors, but the most important remains the laboratory's seriousness: its accreditation, quality procedures, and the way samples and data are managed.

In this guide, we explain:

• what accreditation is,

• what ISO/IEC 17025 guarantees,

• the main risks that can affect a DNA test,

• how to secure collection,

• which tests to favour according to your situation,

• and why indirect tests require more precautions.

What is accreditation?

An accreditation is official recognition of an organisation's competence in a given field.

It serves to demonstrate that a laboratory:

• meets technical requirements,

• applies a quality management system,

• follows controlled procedures,

• produces reproducible results.

In practice, accreditation is a key indicator for judging a laboratory's level of seriousness.

Genetic accreditation: ISO and ISO/IEC 17025

ISO: the organisation that publishes international standards

The International Organization for Standardization (ISO) is a non-governmental organisation that develops international standards in many sectors.

These standards are useful for both public and private organisations, and also protect consumers by imposing quality and control requirements.

ISO/IEC 17025 standard: the reference for laboratories

The ISO/IEC 17025 standard defines general requirements concerning the competence of testing and calibration laboratories.

It particularly covers:

• staff competence,

• traceability and rigour of procedures,

• maintenance and control of equipment,

• organisation of data production processes,

• capacity to produce reliable results.

This standard also promotes cooperation between laboratories, information exchange, and harmonisation of methods.

In summary: recognised accreditation is a strong indicator that a laboratory is capable of producing reliable results, according to high quality standards.

DNA test reliability: factors that really matter

A DNA test is a comparison of genetic profiles performed according to a strict protocol. In the laboratory, comparison is generally controlled and verified, which strongly limits irregularities.

However, reliability can depend on several elements.

1) Laboratory accreditation and procedures

An accredited laboratory follows standardised and verified protocols. This reduces risks of analysis error.

In most cases, when a problem occurs, it's often related to errors upstream.

2) Identification or labelling errors (a more frequent risk)

The most common problems don't come from the "machine", but from test organisation:

• sample inversion,

• poor participant identification,

• confusion when completing documents,

• non-compliant collection.

Important advice: be very rigorous when declaring and organising collections, to avoid uncertainties.

Participant declaration: a key point (often underestimated)

Before ordering, it's strongly recommended to explain your situation to the laboratory.

Genetics touches intimacy and family links. A detail can change:

• test choice,

• necessary participants,

• and therefore reliability.

Concrete example

A paternity search between a father and daughter can, apparently, be done with a simple paternity test.

But if the doubt concerns another man from the same family as the father (for example a brother), then:

• both presumed fathers must participate,

• otherwise the test can become impossible,

• or only achievable with additional participants (for example the mother), with sometimes reduced reliability depending on the case.

Without prior advice, it's difficult to guarantee the chosen test will correctly answer your question.

How to secure genetic collection?

Engage a doctor to supervise collections

If you don't have control over collections (distant participants, doubts about compliance with instructions, risk of falsification), you can engage a doctor to supervise the procedure.

In this case:

1. You contact a doctor beforehand to explain the procedure.

2. The doctor can receive the kit directly from the laboratory.

3. The doctor summons participants.

4. The doctor verifies:

   • participants' identity,

   • compliance with instructions,

   • necessary documents,

   • sample packaging.

5. The doctor can also organise return to the laboratory.

This supervision provides:

• more rigour in collection,

• identity verification,

• better confidence in the result,

• reduction of sample exchange risk.

This solution is particularly useful when participants are in different countries.

Type of genetic test: direct vs indirect

Not all DNA tests give the same level of certainty.

Direct tests (to favour when possible)

As a general rule, it's advisable to do a DNA test directly with the person concerned (presumed father, presumed mother, etc.).

This allows a clearer answer to be obtained, with generally stronger results.

Tests we recommend favouring

Paternity test

If the father is available, favour this test.

• reliability: 100% in case of negative result,

• reliability: approximately 99% (or more depending on laboratories) in case of positive result.

Maternity test

If the mother is available, favour this test.

• reliability: 100% in case of negative result,

• reliability: approximately 99% (or more depending on laboratories) in case of positive result.

Y-chromosome test

It allows verification of whether two men belong to the same paternal line (transmission from father to son).

• reliability: 100% in case of negative result,

• reliability: approximately 99% in case of positive result.

X-chromosome test

It can help in certain paternity searches between sisters.

The X chromosome inherited from the father must be identical between biological sisters. This can also apply between paternal grandmother and her granddaughter.

Mitochondrial DNA test (mtDNA)

It allows verification of whether two people belong to the same maternal line, as mitochondrial DNA is transmitted identically from mother to all her children.

• reliability: 100% in case of negative result,

• reliability: approximately 99% in case of positive result.

Prenatal paternity test

During pregnancy, comparison must necessarily be made between mother and presumed father. In this case, comparison is direct, and reliability is comparable to standard paternity testing.

Indirect tests (reliable, but more context-dependent)

If you cannot directly test the person concerned, it's sometimes possible to do indirect tests with other family members.

These tests rely more on probabilities and statistics. This doesn't mean the test is "false", but that the result may be less conclusive depending on cases.

Reliability depends greatly on:

• the initial family situation,

• number of participants,

• and quality of information provided.

Examples of indirect tests

Siblingship test

To increase reliability:

• specify whether it's full siblingship or half-siblingship,

• if possible compare people of opposite sexes,

• if possible include the mother(s).

Avuncular test (uncle / aunt)

To increase reliability:

• be certain of the biological relationship between the sought parent and their sister or brother,

• if possible include the child's mother.

Grandparentage test

To increase reliability:

• be certain of the biological relationship between the sought parent and their own parents,

• both grandparents must participate,

• if possible include the child's mother.

Type of DNA sample: standard vs non-standard

Final reliability doesn't depend "solely" on sample type, but not all samples are equivalent for extracting DNA.

The laboratory's first difficulty is extracting usable DNA.

In practice, buccal swabs offer very good extraction reliability if instructions are followed.

It's sometimes possible to use non-standard samples, less reliable, but useful when saliva collection isn't feasible.

How to verify that a DNA laboratory is accredited?

A test's reliability (genealogy or relationship) depends on the laboratory's expertise.

To ensure seriousness:

• verify accreditation,

• request, if needed, a recent certificate,

• also verify data protection policy.