How to interpret genetic test results

The first step: understanding what test was performed

Not all genetic tests examine the same things. Some analyze the number and structure of chromosomes. Others examine specific regions of DNA, one or more genes, the exome, or the whole genome. There are also tests designed to evaluate gene expression or other aspects of gene function.

Before interpreting any result, it is therefore essential to understand what type of genetic test was performed and what its scope was.

A karyotype, for example, can detect relatively large changes in the number or structure of chromosomes. Other tests may detect smaller losses or gains of DNA. Sequencing tests, in contrast, can identify changes in the DNA sequence of one or more genes. Each technology addresses different questions and has its own capabilities and limitations. This means that a normal or negative result on a particular test does not necessarily rule out a genetic cause. If you want a refresher on the main types of tests, see our guide on what a genetic test is.

Understanding what the laboratory actually found

The next step is to identify what finding the laboratory reported and what it means within the context of the specific test that was performed.

Depending on the test, the report may describe changes in chromosome number, alterations in chromosome structure, losses or gains of genetic material, changes in one or more genes, modifications in the DNA sequence, or differences in the activity of certain genes.

The first question, therefore, should not simply be, "Is the result positive or negative?" but rather: what exactly did the test find, and what could that finding mean?

It is also important to distinguish between what the laboratory directly observed and the interpretation made from that finding. A result may be technically very clear while its relevance to the patient's condition remains uncertain.

A conclusive result

In some cases, the test identifies a well-established genetic alteration that is clearly related to the condition being investigated. When this occurs, the result may make an important contribution to establishing or confirming a diagnosis.

However, even an apparently straightforward result should be interpreted together with the patient's medical history, symptoms, family history, and other clinical findings. The presence of a genetic alteration does not always produce exactly the same manifestations in every individual: the age at which symptoms appear, their severity, and the organs or systems affected may vary even among people with similar genetic changes.

For this reason, the molecular result should always be considered as one part of the overall clinical evaluation.

What a negative result means

A negative result means that the test did not identify an alteration considered relevant within the regions and types of changes it was designed to examine.

However, a negative result does not necessarily mean that the condition has no genetic cause.

There are several reasons why a test may fail to identify the cause of a disease:

• The relevant alteration may be located in a region of DNA that the test does not adequately examine.
• It may be a type of change that is difficult to detect with the technology used.
• The gene responsible for the condition may not yet have been identified, or the underlying molecular mechanism may still be poorly understood.
• Some diseases do not result from a single genetic change but from interactions between multiple genes and environmental factors.

Interpreting a negative result therefore requires a clear understanding of exactly what the test analyzed and what its limitations were.

When the result remains inconclusive

Some genetic tests identify findings that do not allow a definitive conclusion to be reached.

This type of result can be particularly frustrating for patients, families, and physicians, especially when the clinical features strongly suggest a specific disease. One situation commonly encountered in sequencing studies is the identification of a Variant of Uncertain Significance (VUS): a change in DNA for which the available scientific evidence is not sufficient to determine with adequate certainty whether it is related to the disease or simply represents part of normal genetic variation.

The presence of a VUS does not mean that the test was performed incorrectly. It means that the scientific knowledge available at that time is not sufficient to establish a definitive relationship between the finding and the disease. We have a dedicated guide on understanding VUS results.

Can an inconclusive result be analyzed in greater depth?

In selected cases, yes.

When a finding is complex or inconclusive, it may be useful to review additional scientific information and analytical tools that are not necessarily explored in detail in the original laboratory report. For a VUS, for example, elements such as its frequency in different populations, published studies, functional data, characteristics of the gene and its protein, family information, and different bioinformatic analyses can be considered.

The goal is not to assume that an uncertain finding causes the disease, but to determine whether additional information exists that can help clarify its possible relevance. In some cases, this analysis may provide additional scientific arguments that help connect the result to the clinical situation. In others, the uncertainty may remain.

Clinical context is essential

A genetic result should not be interpreted in isolation. Understanding its significance requires considering information such as:

• the patient's symptoms;
• the age at which they appeared;
• the organs or systems affected;
• how the condition has evolved;
• family history;
• the results of other studies;
• and the clinical suspicion that motivated the test in the first place.

The same finding can have a different relevance depending on the context in which it appears. For this reason, genetic interpretation and clinical evaluation must complement each other.

Understanding the limitations of the test

All genetic tests have limitations. Each test is designed to analyze certain types of alterations and certain regions of the genetic material. No test can identify absolutely every possible change in DNA or explain every disease.

A gene panel studies only the selected genes. An exome mainly analyzes the coding regions of genes. A whole genome allows a much larger proportion of DNA to be studied, but it still does not guarantee that all alterations can be detected or correctly interpreted. In addition, there may be genetic information that we do not yet understand scientifically.

An essential part of interpretation, therefore, is understanding what the test was able to evaluate, what it could not evaluate, and which questions remain open.

Interpretation can change over time

Genetics is a constantly evolving discipline. Every year, new disease-related genes are described, new studies are published, and information accumulates about previously identified alterations.

This means that a result that is inconclusive today may be interpreted differently in the future. For this reason, some genetic results can benefit from a later review, especially when there is a strong clinical suspicion and the original test did not provide a clear explanation.

Can a genetic result influence treatment?

In certain conditions, yes. In some diseases, identifying a specific molecular alteration can help select certain treatments, establish follow-up strategies, or indicate testing for other family members. Genetics can also help explain individual differences in the response to certain medications, a field known as pharmacogenetics or pharmacogenomics.

However, treatment decisions must always be made by the treating physician, taking into account all the available clinical information.

Why genetic reports can be so difficult to understand

Genetic reports are written primarily as technical documents. They may include concepts related to chromosomes, genes, inheritance patterns, variants, sequencing, coverage, deletions, duplications, or inconclusive results, among others.

For a person without training in genetics, these terms can be difficult to understand. Even some healthcare professionals who do not routinely work in genetics may find certain reports especially complex. In addition, a laboratory may describe a finding correctly from a technical standpoint without explaining in detail what it means for the patient, which questions the test answers, and which remain unanswered.

For this reason, explaining a genetic test in understandable language is an important part of its correct interpretation. If your result has caused you anxiety or confusion, our guide on fear and frustration after genetic test results may help.

Useful questions when reviewing a genetic result

When you receive a report, it can be helpful to try to answer some fundamental questions:

• What type of test was performed?
• What information did it analyze?
• What exactly did it find?
• Is the result conclusive, negative, or inconclusive?
• What can the finding explain, and what can it not explain?
• What are the limitations of the test?
• Is there information that could be analyzed in greater depth?
• Could the result have implications for other family members?
• Could it be relevant for follow-up or treatment?

Answering these questions helps transform a highly technical report into clearer, more useful information.

Frequently asked questions